CWE-436: Interpretation Conflict

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.

Extended Description

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.

Related Weaknesses

Modes of Introduction

Applicable Platforms

Languages

Class: Not Language-Specific

Technologies

Common Consequences

Observed 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.