CWE

Common Weakness Enumeration

A Community-Developed List of Software Weakness Types

CWE/SANS Top 25 Most Dangerous Software Errors
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ID

CWE-41: Improper Resolution of Path Equivalence

Weakness ID: 41
Abstraction: Base
Structure: Simple
Status: Incomplete
Presentation Filter:
+ Description
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.
+ Relationships

The table(s) below 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.

+ Modes Of Introduction

The different Modes of Introduction provide information about how and when this weakness may be introduced. The Phase identifies a point in the software 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
The listings below show 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

(Language-Independent classes): (Undetermined Prevalence)

+ Common Consequences

The table below 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
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.
+ 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.
+ Detection Methods

Automated Static Analysis - Binary or 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 or 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: 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 or 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: High

+ Affected Resources
  • File or Directory
+ Memberships
This 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.
+ Notes

Relationship

Some of these manipulations could be effective in path traversal issues, too.
+ Taxonomy Mappings
Mapped Taxonomy NameNode IDFitMapped Node Name
PLOVERPath Equivalence
CERT C Secure CodingFIO02-CCanonicalize path names originating from untrusted sources
+ Content History
Submissions
Submission DateSubmitterOrganizationSource
PLOVER
Modifications
Modification DateModifierOrganizationSource
2008-07-01Eric DalciCigital
updated Potential_Mitigations, Time_of_Introduction
2008-09-08CWE Content TeamMITRE
updated Relationships, Other_Notes, Taxonomy_Mappings, Type
2008-10-14CWE Content TeamMITRE
updated Description
2008-11-24CWE Content TeamMITRE
updated Relationships, Taxonomy_Mappings
2009-03-10CWE Content TeamMITRE
updated Relationships
2009-05-27CWE Content TeamMITRE
updated Name
2009-07-27CWE Content TeamMITRE
updated Potential_Mitigations
2011-03-29CWE Content TeamMITRE
updated Other_Notes, Potential_Mitigations, Relationship_Notes
2011-06-01CWE Content TeamMITRE
updated Common_Consequences
2011-09-13CWE Content TeamMITRE
updated Relationships, Taxonomy_Mappings
2012-05-11CWE Content TeamMITRE
updated Common_Consequences, Observed_Examples, Relationships
2012-10-30CWE Content TeamMITRE
updated Potential_Mitigations
2014-07-30CWE Content TeamMITRE
updated Detection_Factors, Relationships
2017-11-08CWE Content TeamMITRE
updated Affected_Resources, Applicable_Platforms, Relationships, Taxonomy_Mappings
Previous Entry Names
Change DatePrevious Entry Name
2008-04-11Path Equivalence
2009-05-27Failure to Resolve Path Equivalence

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Page Last Updated: November 14, 2017