Improper Resolution of Path Equivalence
Incomplete Base
Structure: Simple
Description
This vulnerability occurs when an application fails to properly handle different text representations that refer to the same file or directory on the system. Attackers can use special characters or alternative naming conventions to bypass security checks and access restricted files.
Path equivalence flaws happen because security logic often checks for only one specific name or path format. Attackers exploit this by using alternative representations—like trailing dots, extra slashes, or case variations—that the operating system treats as identical but the application's filters miss. This allows them to read sensitive files they shouldn't have access to, differing from path traversal where the attacker targets a completely different file. Detecting these subtle logic gaps manually is challenging, especially in complex codebases. While SAST tools can flag the pattern, Plexicus uses AI to analyze the specific context and generate the precise code fix needed to normalize and validate all path inputs, helping teams remediate these flaws efficiently across their entire application portfolio.
Common Consequences 1
Scope: ConfidentialityIntegrityAccess Control
Impact: Read Files or DirectoriesModify Files or DirectoriesBypass 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 7
Automated Static Analysis - Binary or BytecodeSOAR Partial
According to SOAR [REF-1479], the following detection techniques may be useful:
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Cost effective for partial coverage:
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Bytecode Weakness Analysis - including disassembler + source code weakness analysisManual Static Analysis - Binary or BytecodeSOAR Partial
According to SOAR [REF-1479], the following detection techniques may be useful:
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Cost effective for partial coverage:
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Binary / Bytecode disassembler - then use manual analysis for vulnerabilities & anomaliesDynamic Analysis with Automated Results InterpretationSOAR Partial
According to SOAR [REF-1479], the following detection techniques may be useful:
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Cost effective for partial coverage:
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Web Application Scanner
Web Services Scanner
Database ScannersDynamic Analysis with Manual Results InterpretationSOAR Partial
According to SOAR [REF-1479], the following detection techniques may be useful:
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Cost effective for partial coverage:
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Fuzz Tester
Framework-based FuzzerManual Static Analysis - Source CodeHigh
According to SOAR [REF-1479], the following detection techniques may be useful:
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Highly cost effective:
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Focused Manual Spotcheck - Focused manual analysis of source
Manual Source Code Review (not inspections)Automated Static Analysis - Source CodeSOAR Partial
According to SOAR [REF-1479], the following detection techniques may be useful:
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Cost effective for partial coverage:
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Source code Weakness Analyzer
Context-configured Source Code Weakness AnalyzerArchitecture or Design ReviewHigh
According to SOAR [REF-1479], the following detection techniques may be useful:
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Highly cost effective:
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Formal Methods / Correct-By-Construction
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Cost effective for partial coverage:
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Inspection (IEEE 1028 standard) (can apply to requirements, design, source code, etc.)Potential Mitigations 3
Phase: Implementation
Strategy: Input Validation
Assume all input is malicious. Use an "accept known good" input validation strategy, i.e., use a list 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. This 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, denylists 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 (Incorrect Behavior Order: Validate Before Canonicalize). Make sure that the application does not decode the same input twice (Double Decoding of the Same Data). Such errors could be used to bypass allowlist validation schemes by introducing dangerous inputs after they have been checked.
Observed Examples 50
CVE-2000-1114Source code disclosure using trailing dot
CVE-2002-1986Source code disclosure using trailing dot
CVE-2004-2213Source code disclosure using trailing dot or trailing encoding space "%20"
CVE-2005-3293Source code disclosure using trailing dot
CVE-2004-0061Bypass directory access restrictions using trailing dot in URL
CVE-2000-1133Bypass directory access restrictions using trailing dot in URL
CVE-2001-1386Bypass check for ".lnk" extension using ".lnk."
CVE-2001-0693Source disclosure via trailing encoded space "%20"
CVE-2001-0778Source disclosure via trailing encoded space "%20"
CVE-2001-1248Source disclosure via trailing encoded space "%20"
CVE-2004-0280Source disclosure via trailing encoded space "%20"
CVE-2005-0622Source disclosure via trailing encoded space "%20"
CVE-2005-1656Source disclosure via trailing encoded space "%20"
CVE-2002-1603Source disclosure via trailing encoded space "%20"
CVE-2001-0054Multi-Factor Vulnerability (MFV). directory traversal and other issues in FTP server using Web encodings such as "%20"; certain manipulations have unusual side effects.
CVE-2002-1451Trailing space ("+" in query string) leads to source code disclosure.
CVE-2000-0293Filenames with spaces allow arbitrary file deletion when the product does not properly quote them; some overlap with path traversal.
CVE-2001-1567"+" characters in query string converted to spaces before sensitive file/extension (internal space), leading to bypass of access restrictions to the file.
CVE-2002-0253Overlaps infoleak
CVE-2001-0446Application server allows remote attackers to read source code for .jsp files by appending a / to the requested URL.
CVE-2004-0334Bypass Basic Authentication for files using trailing "/"
CVE-2001-0893Read sensitive files with trailing "/"
CVE-2001-0892Web server allows remote attackers to view sensitive files under the document root (such as .htpasswd) via a GET request with a trailing /.
CVE-2004-1814Directory traversal vulnerability in server allows remote attackers to read protected files via .. (dot dot) sequences in an HTTP request.
CVE-2002-1483Read files with full pathname using multiple internal slash.
CVE-1999-1456Server allows remote attackers to read arbitrary files via a GET request with more than one leading / (slash) character in the filename.
CVE-2004-0578Server allows remote attackers to read arbitrary files via leading slash (//) characters in a URL request.
CVE-2002-0275Server allows remote attackers to bypass authentication and read restricted files via an extra / (slash) in the requested URL.
CVE-2004-1032Product allows local users to delete arbitrary files or create arbitrary empty files via a target filename with a large number of leading slash (/) characters.
CVE-2002-1238Server 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/.
CVE-2004-1878Product 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).
CVE-2005-1365Server allows remote attackers to execute arbitrary commands via a URL with multiple leading "/" (slash) characters and ".." sequences.
CVE-2000-1050Access directory using multiple leading slash.
CVE-2001-1072Bypass access restrictions via multiple leading slash, which causes a regular expression to fail.
CVE-2004-0235Archive extracts to arbitrary files using multiple leading slash in filenames in the archive.
CVE-2002-1078Directory listings in web server using multiple trailing slash
CVE-2004-0847ASP.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."
CVE-2000-0004Server allows remote attackers to read source code for executable files by inserting a . (dot) into the URL.
CVE-2002-0304Server allows remote attackers to read password-protected files via a /./ in the HTTP request.
CVE-1999-1083Possibly (could be a cleansing error)
CVE-2004-0815"/./////etc" cleansed to ".///etc" then "/etc"
CVE-2002-0112Server allows remote attackers to view password protected files via /./ in the URL.
CVE-2004-0696List directories using desired path and "*"
CVE-2002-0433List files in web server using "*.ext"
CVE-2001-1152Proxy allows remote attackers to bypass denylist 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.
CVE-2000-0191application check access for restricted URL before canonicalization
CVE-2005-1366CGI source disclosure using "dirname/../cgi-bin"
CVE-1999-0012Multiple web servers allow restriction bypass using 8.3 names instead of long names
CVE-2001-0795Source code disclosure using 8.3 file name.
CVE-2005-0471Multi-Factor Vulnerability. Product generates temporary filenames using long filenames, which become predictable in 8.3 format.
References 1
State-of-the-Art Resources (SOAR) for Software Vulnerability Detection, Test, and Evaluation
Gregory Larsen, E. Kenneth Hong Fong, David A. Wheeler, and Rama S. Moorthy
07-2014
ID: REF-1479
Applicable Platforms
Languages:
Not Language-Specific : Undetermined
Modes of Introduction
Implementation
Related Attack Patterns
Functional Areas
- File Processing
Affected Resources
- File or Directory
Related Weaknesses
Taxonomy Mapping
- PLOVER
- CERT C Secure Coding
Notes
RelationshipSome of these manipulations could be effective in path traversal issues, too.