Collapse of Data Into Unsafe Value
Weakness ID: 182 (Weakness Base)Status: Draft
+ Description

Description Summary

The software cleanses or filters data in a way that causes the data to be reduced or "collapsed" into an unsafe value.
+ Time of Introduction
  • Implementation
+ Applicable Platforms



+ Observed Examples
CVE-2004-0815"/.////" in pathname collapses to absolute path.
CVE-2005-3123"/.//..//////././" is collapsed into "/.././" after ".." and "//" sequences are removed.
CVE-2002-0325".../...//" collapsed to "..." due to removal of "./" in web server.
CVE-2002-0784chain: HTTP server protects against ".." but allows "." variants such as "////./../.../". If the server removes "/.." sequences, the result would collapse into an unsafe value "////../" (CWE-182).
CVE-2005-2169MFV. Regular expression intended to protect against directory traversal reduces ".../...//" to "../".
+ Potential Mitigations

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

Phase: Architecture and Design

Assume all input is malicious. Use a standard input validation mechanism to validate all input for length, type, syntax, and business rules before accepting the data to be displayed or stored. Use an "accept known good" validation strategy.

Use and specify a strong output encoding (such as ISO 8859-1 or UTF 8).

Do not rely exclusively on blacklist validation to detect malicious input or to encode output. There are too many variants to encode a character; you're likely to miss some variants.

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

Canonicalize the name to match that of the file system's representation of the name. This can sometimes be achieved with an available API (e.g. in Win32 the GetFullPathName function).

+ Relationships
NatureTypeIDNameView(s) this relationship pertains toView(s)
ChildOfCategoryCategory171Cleansing, Canonicalization, and Comparison Errors
Development Concepts (primary)699
ChildOfWeakness ClassWeakness Class693Protection Mechanism Failure
Research Concepts (primary)1000
ChildOfCategoryCategory722OWASP Top Ten 2004 Category A1 - Unvalidated Input
Weaknesses in OWASP Top Ten (2004) (primary)711
CanPrecedeWeakness VariantWeakness Variant33Path Traversal: '....' (Multiple Dot)
Research Concepts1000
CanPrecedeWeakness VariantWeakness Variant34Path Traversal: '....//'
Research Concepts1000
CanPrecedeWeakness VariantWeakness Variant35Path Traversal: '.../...//'
Research Concepts1000
CanFollowWeakness ClassWeakness Class185Incorrect Regular Expression
Research Concepts1000
+ Relationship Notes

Overlaps regular expressions, although an implementation might not necessarily use regexp's.

+ Relevant Properties
  • Trustability
+ Taxonomy Mappings
Mapped Taxonomy NameNode IDFitMapped Node Name
PLOVERCollapse of Data into Unsafe Value
+ Content History
Submission DateSubmitterOrganizationSource
PLOVERExternally Mined
Modification DateModifierOrganizationSource
2008-07-01Eric DalciCigitalExternal
updated Potential Mitigations, Time of Introduction
2008-09-08CWE Content TeamMITREInternal
updated Description, Relationships, Relationship Notes, Relevant Properties, Taxonomy Mappings
2008-11-24CWE Content TeamMITREInternal
updated Observed Examples
2009-03-10CWE Content TeamMITREInternal
updated Relationships
2009-07-27CWE Content TeamMITREInternal
updated Potential Mitigations