Description

Product A handles inputs or steps differently than Product B, which causes A to perform incorrect actions based on its perception of B’s state.

This is generally found in proxies, firewalls, anti-virus software, and other intermediary devices that monitor, allow, deny, or modify traffic based on how the client or server is expected to behave.

Modes of Introduction:

– Architecture and Design

Related Weaknesses

CWE-435

Consequences

Integrity, Other: Unexpected State, Varies by Context

Potential Mitigations

CVE References

• CVE-2005-1215
  • Bypass filters or poison web cache using requests with multiple Content-Length headers, a non-standard behavior.

• CVE-2002-0485
  • Anti-virus product allows bypass via Content-Type and Content-Disposition headers that are mixed case, which are still processed by some clients.

• CVE-2002-1978
  • FTP clients sending a command with “PASV” in the argument can cause firewalls to misinterpret the server’s error as a valid response, allowing filter bypass.

• CVE-2002-1979
  • FTP clients sending a command with “PASV” in the argument can cause firewalls to misinterpret the server’s error as a valid response, allowing filter bypass.

• CVE-2002-0637
  • Virus product bypass with spaces between MIME header fields and the “:” separator, a non-standard message that is accepted by some clients.

• CVE-2002-1777
  • AV product detection bypass using inconsistency manipulation (file extension in MIME Content-Type vs. Content-Disposition field).

• CVE-2005-3310
  • CMS system allows uploads of files with GIF/JPG extensions, but if they contain HTML, Internet Explorer renders them as HTML instead of images.

• CVE-2005-4260
  • Interpretation conflict allows XSS via invalid “” is expected, which is treated as “>” by many web browsers.

• CVE-2005-4080
  • Interpretation conflict (non-standard behavior) enables XSS because browser ignores invalid characters in the middle of tags.