CWE WEAKNESSES  /  CWE-436

CWE-436

Interpretation Conflict

What it is

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.

Impact

Real-world CVE examples

• 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 "<" when a ">" 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.

Related weaknesses

Source: MITRE CWE. View on cwe.mitre.org →