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Common Weakness Enumeration

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ID

CWE-121: Stack-based Buffer Overflow

Weakness ID: 121
Abstraction: Variant
Structure: Simple
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+ Description
A stack-based buffer overflow condition is a condition where the buffer being overwritten is allocated on the stack (i.e., is a local variable or, rarely, a parameter to a function).
+ Alternate Terms
Stack Overflow:
"Stack Overflow" is often used to mean the same thing as stack-based buffer overflow, however it is also used on occasion to mean stack exhaustion, usually a result from an excessively recursive function call. Due to the ambiguity of the term, use of stack overflow to describe either circumstance is discouraged.
+ Relationships
Section HelpThis table shows the weaknesses and high level categories that are related to this weakness. These relationships are defined as ChildOf, ParentOf, MemberOf and give insight to similar items that may exist at higher and lower levels of abstraction. In addition, relationships such as PeerOf and CanAlsoBe are defined to show similar weaknesses that the user may want to explore.
+ Relevant to the view "Research Concepts" (CWE-1000)
NatureTypeIDName
ChildOfBaseBase - a weakness that is still mostly independent of a resource or technology, but with sufficient details to provide specific methods for detection and prevention. Base level weaknesses typically describe issues in terms of 2 or 3 of the following dimensions: behavior, property, technology, language, and resource.787Out-of-bounds Write
ChildOfBaseBase - a weakness that is still mostly independent of a resource or technology, but with sufficient details to provide specific methods for detection and prevention. Base level weaknesses typically describe issues in terms of 2 or 3 of the following dimensions: behavior, property, technology, language, and resource.788Access of Memory Location After End of Buffer
+ Background Details
There are generally several security-critical data on an execution stack that can lead to arbitrary code execution. The most prominent is the stored return address, the memory address at which execution should continue once the current function is finished executing. The attacker can overwrite this value with some memory address to which the attacker also has write access, into which they place arbitrary code to be run with the full privileges of the vulnerable program. Alternately, the attacker can supply the address of an important call, for instance the POSIX system() call, leaving arguments to the call on the stack. This is often called a return into libc exploit, since the attacker generally forces the program to jump at return time into an interesting routine in the C standard library (libc). Other important data commonly on the stack include the stack pointer and frame pointer, two values that indicate offsets for computing memory addresses. Modifying those values can often be leveraged into a "write-what-where" condition.
+ Modes Of Introduction
Section HelpThe different Modes of Introduction provide information about how and when this weakness may be introduced. The Phase identifies a point in the life cycle at which introduction may occur, while the Note provides a typical scenario related to introduction during the given phase.
PhaseNote
Implementation
+ Applicable Platforms
Section HelpThis listing shows possible areas for which the given weakness could appear. These may be for specific named Languages, Operating Systems, Architectures, Paradigms, Technologies, or a class of such platforms. The platform is listed along with how frequently the given weakness appears for that instance.

Languages

C (Undetermined Prevalence)

C++ (Undetermined Prevalence)

+ Common Consequences
Section HelpThis table specifies different individual consequences associated with the weakness. The Scope identifies the application security area that is violated, while the Impact describes the negative technical impact that arises if an adversary succeeds in exploiting this weakness. The Likelihood provides information about how likely the specific consequence is expected to be seen relative to the other consequences in the list. For example, there may be high likelihood that a weakness will be exploited to achieve a certain impact, but a low likelihood that it will be exploited to achieve a different impact.
ScopeImpactLikelihood
Availability

Technical Impact: Modify Memory; DoS: Crash, Exit, or 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: Modify Memory; Execute Unauthorized Code or Commands; Bypass Protection Mechanism

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

Technical Impact: Modify Memory; 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
+ Demonstrative Examples

Example 1

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

(bad code)
Example Language:
#define BUFSIZE 256
int main(int argc, char **argv) {
char buf[BUFSIZE];
strcpy(buf, argv[1]);
}

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

Example 2

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 the function 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).

+ Observed Examples
ReferenceDescription
Stack-based buffer overflows in SFK for wifi chipset used for IoT/embedded devices, as exploited in the wild per CISA KEV.
+ Potential Mitigations

Phases: Operation; Build and Compilation

Strategy: Environment Hardening

Use automatic buffer overflow detection mechanisms that are offered by certain compilers or compiler extensions. Examples include: the Microsoft Visual Studio /GS flag, Fedora/Red Hat FORTIFY_SOURCE GCC flag, StackGuard, and ProPolice, which provide various mechanisms including canary-based detection and range/index checking.

D3-SFCV (Stack Frame Canary Validation) from D3FEND [REF-1334] discusses canary-based detection in detail.

Effectiveness: Defense in Depth

Note:

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

Phase: Architecture and Design

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

Phase: Implementation

Implement and perform bounds checking on input.

Phase: Implementation

Do not use dangerous functions such as gets. Use safer, equivalent functions which check for boundary errors.

Phases: Operation; Build and Compilation

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) [REF-58] [REF-60] and Position-Independent Executables (PIE) [REF-64]. Imported modules may be similarly realigned if their default memory addresses conflict with other modules, in a process known as "rebasing" (for Windows) and "prelinking" (for Linux) [REF-1332] using randomly generated addresses. ASLR for libraries cannot be used in conjunction with prelink since it would require relocating the libraries at run-time, defeating the whole purpose of prelinking.

For more information on these techniques see D3-SAOR (Segment Address Offset Randomization) from D3FEND [REF-1335].

Effectiveness: Defense in Depth

Note: These techniques do not provide a complete solution. For instance, exploits frequently use a bug that discloses memory addresses in order to maximize reliability of code execution [REF-1337]. It has also been shown that a side-channel attack can bypass ASLR [REF-1333]
+ Weakness Ordinalities
OrdinalityDescription
Primary
(where the weakness exists independent of other weaknesses)
+ Detection Methods

Fuzzing

Fuzz testing (fuzzing) is a powerful technique for generating large numbers of diverse inputs - either randomly or algorithmically - and dynamically invoking the code with those inputs. Even with random inputs, it is often capable of generating unexpected results such as crashes, memory corruption, or resource consumption. Fuzzing effectively produces repeatable test cases that clearly indicate bugs, which helps developers to diagnose the issues.

Effectiveness: High

Automated Static Analysis

Automated static analysis, commonly referred to as Static Application Security Testing (SAST), can find some instances of this weakness by analyzing source code (or binary/compiled code) without having to execute it. Typically, this is done by building a model of data flow and control flow, then searching for potentially-vulnerable patterns that connect "sources" (origins of input) with "sinks" (destinations where the data interacts with external components, a lower layer such as the OS, etc.)

Effectiveness: High

+ Memberships
Section HelpThis MemberOf Relationships table shows additional CWE Categories and Views that reference this weakness as a member. This information is often useful in understanding where a weakness fits within the context of external information sources.
NatureTypeIDName
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.970SFP Secondary Cluster: Faulty Buffer Access
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.1160SEI CERT C Coding Standard - Guidelines 06. Arrays (ARR)
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.1161SEI CERT C Coding Standard - Guidelines 07. Characters and Strings (STR)
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.1365ICS Communications: Unreliability
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.1366ICS Communications: Frail Security in Protocols
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.1399Comprehensive Categorization: Memory Safety
+ Vulnerability Mapping Notes

Usage: Allowed

(this CWE ID could be used to map to real-world vulnerabilities)

Reason: Acceptable-Use

Rationale:

This CWE entry is at the Variant level of abstraction, which is a preferred level of abstraction for mapping to the root causes of vulnerabilities.

Comments:

Carefully read both the name and description to ensure that this mapping is an appropriate fit. Do not try to 'force' a mapping to a lower-level Base/Variant simply to comply with this preferred level of abstraction.
+ Notes

Other

Stack-based buffer overflows can instantiate in return address overwrites, stack pointer overwrites or frame pointer overwrites. They can also be considered function pointer overwrites, array indexer overwrites or write-what-where condition, etc.
+ Taxonomy Mappings
Mapped Taxonomy NameNode IDFitMapped Node Name
CLASPStack overflow
Software Fault PatternsSFP8Faulty Buffer Access
CERT C Secure CodingARR38-CImpreciseGuarantee that library functions do not form invalid pointers
CERT C Secure CodingSTR31-CCWE More SpecificGuarantee that storage for strings has sufficient space for character data and the null terminator
+ References
[REF-1029] Aleph One. "Smashing The Stack For Fun And Profit". 1996-11-08. <http://phrack.org/issues/49/14.html>.
[REF-7] Michael Howard and David LeBlanc. "Writing Secure Code". Chapter 5, "Stack Overruns" Page 129. 2nd Edition. Microsoft Press. 2002-12-04. <https://www.microsoftpressstore.com/store/writing-secure-code-9780735617223>.
[REF-44] Michael Howard, David LeBlanc and John Viega. "24 Deadly Sins of Software Security". "Sin 5: Buffer Overruns." Page 89. McGraw-Hill. 2010.
[REF-62] 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-62] Mark Dowd, John McDonald and Justin Schuh. "The Art of Software Security Assessment". Chapter 5, "Protection Mechanisms", Page 189. 1st Edition. Addison Wesley. 2006.
[REF-18] Secure Software, Inc.. "The CLASP Application Security Process". 2005. <https://cwe.mitre.org/documents/sources/TheCLASPApplicationSecurityProcess.pdf>.
[REF-58] Michael Howard. "Address Space Layout Randomization in Windows Vista". <https://learn.microsoft.com/en-us/archive/blogs/michael_howard/address-space-layout-randomization-in-windows-vista>. URL validated: 2023-04-07.
[REF-60] "PaX". <https://en.wikipedia.org/wiki/Executable_space_protection#PaX>. URL validated: 2023-04-07.
[REF-64] Grant Murphy. "Position Independent Executables (PIE)". Red Hat. 2012-11-28. <https://www.redhat.com/en/blog/position-independent-executables-pie>. URL validated: 2023-04-07.
[REF-1332] John Richard Moser. "Prelink and address space randomization". 2006-07-05. <https://lwn.net/Articles/190139/>. URL validated: 2023-04-26.
[REF-1333] Dmitry Evtyushkin, Dmitry Ponomarev, Nael Abu-Ghazaleh. "Jump Over ASLR: Attacking Branch Predictors to Bypass ASLR". 2016. <http://www.cs.ucr.edu/~nael/pubs/micro16.pdf>. URL validated: 2023-04-26.
[REF-1334] D3FEND. "Stack Frame Canary Validation (D3-SFCV)". 2023. <https://d3fend.mitre.org/technique/d3f:StackFrameCanaryValidation/>. URL validated: 2023-04-26.
[REF-1335] D3FEND. "Segment Address Offset Randomization (D3-SAOR)". 2023. <https://d3fend.mitre.org/technique/d3f:SegmentAddressOffsetRandomization/>. URL validated: 2023-04-26.
[REF-1337] Alexander Sotirov and Mark Dowd. "Bypassing Browser Memory Protections: Setting back browser security by 10 years". Memory information leaks. 2008. <https://www.blackhat.com/presentations/bh-usa-08/Sotirov_Dowd/bh08-sotirov-dowd.pdf>. URL validated: 2023-04-26.
+ Content History
+ Submissions
Submission DateSubmitterOrganization
2006-07-19
(CWE Draft 3, 2006-07-19)
CLASP
+ Modifications
Modification DateModifierOrganization
2008-07-01Eric DalciCigital
updated Potential_Mitigations, Time_of_Introduction
2008-08-01KDM Analytics
added/updated white box definitions
2008-09-08CWE Content TeamMITRE
updated Alternate_Terms, Applicable_Platforms, Background_Details, Common_Consequences, Relationships, Other_Notes, Taxonomy_Mappings, Weakness_Ordinalities
2009-01-12CWE Content TeamMITRE
updated Common_Consequences, Relationships
2009-07-17KDM Analytics
Improved the White_Box_Definition
2009-07-27CWE Content TeamMITRE
updated Potential_Mitigations, White_Box_Definitions
2009-10-29CWE Content TeamMITRE
updated Relationships
2010-02-16CWE Content TeamMITRE
updated References
2011-06-01CWE Content TeamMITRE
updated Common_Consequences
2012-05-11CWE Content TeamMITRE
updated Demonstrative_Examples, References, Relationships
2012-10-30CWE Content TeamMITRE
updated Demonstrative_Examples, Potential_Mitigations
2014-07-30CWE Content TeamMITRE
updated Relationships, Taxonomy_Mappings
2017-11-08CWE Content TeamMITRE
updated Background_Details, Causal_Nature, Likelihood_of_Exploit, References, Relationships, Taxonomy_Mappings, White_Box_Definitions
2018-03-27CWE Content TeamMITRE
updated References
2019-01-03CWE Content TeamMITRE
updated Relationships
2019-09-19CWE Content TeamMITRE
updated References
2020-02-24CWE Content TeamMITRE
updated Relationships
2020-06-25CWE Content TeamMITRE
updated Common_Consequences
2021-03-15CWE Content TeamMITRE
updated Demonstrative_Examples, References
2021-07-20CWE Content TeamMITRE
updated Demonstrative_Examples
2022-06-28CWE Content TeamMITRE
updated Observed_Examples
2023-04-27CWE Content TeamMITRE
updated Detection_Factors, Potential_Mitigations, References, Relationships, Time_of_Introduction
2023-06-29CWE Content TeamMITRE
updated Mapping_Notes, Relationships
Page Last Updated: October 26, 2023