Description

The software does not properly handle when all or part of an input has been URL encoded.

Modes of Introduction:

– Implementation

Related Weaknesses

CWE-172

Consequences

Integrity: Unexpected State

Potential Mitigations

Phase: Architecture and Design

Description: 

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

Phase: Implementation

Description: 

Phase: Implementation

Description: 

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 allowlist validation schemes by introducing dangerous inputs after they have been checked.

CVE References

• CVE-2000-0900
  • Hex-encoded path traversal variants – “%2e%2e”, “%2e%2e%2f”, “%5c%2e%2e”

• CVE-2005-2256
  • Hex-encoded path traversal variants – “%2e%2e”, “%2e%2e%2f”, “%5c%2e%2e”

• CVE-2004-2121
  • Hex-encoded path traversal variants – “%2e%2e”, “%2e%2e%2f”, “%5c%2e%2e”

• CVE-2004-0280
  • “%20” (encoded space)

• CVE-2003-0424
  • “%20” (encoded space)

• CVE-2001-0693
  • “%20” (encoded space)

• CVE-2001-0778
  • “%20” (encoded space)

• CVE-2002-1831
  • Crash via hex-encoded space “%20”.

• CVE-2000-0671
  • “%00” (encoded null)

• CVE-2004-0189
  • “%00” (encoded null)

• CVE-2002-1291
  • “%00” (encoded null)

• CVE-2002-1031
  • “%00” (encoded null)

• CVE-2001-1140
  • “%00” (encoded null)

• CVE-2004-0760
  • “%00” (encoded null)

• CVE-2002-1025
  • “%00” (encoded null)

• CVE-2002-1213
  • “%2f” (encoded slash)

• CVE-2004-0072
  • “%5c” (encoded backslash) and “%2e” (encoded dot) sequences

• CVE-2004-0847
  • “%5c” (encoded backslash)

• CVE-2002-1575
  • “%0a” (overlaps CRLF)