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CWE - 436 : Interpretation Conflict

CWE Definition
Number of vulnerabilities: 18
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 allow, deny, or modify traffic based on how the client or server is expected to behave.
Background Details
Other Notes The classic multiple interpretation flaws were reported in a paper that described the limitations of intrusion detection systems. Ptacek and Newsham (see references below) showed that OSes varied widely in their behavior with respect to unusual network traffic, which made it difficult or impossible for intrusion detection systems to properly detect certain attacker manipulations that took advantage of the OS differences. Another classic multiple interpretation error is the "poison null byte" described by Rain Forest Puppy (see reference below), in which null characters have different interpretations in Perl and C, which have security consequences when Perl invokes C functions. Similar problems have been reported in ASP (see ASP reference below) and PHP. Some of the more complex web-based attacks, such as HTTP request smuggling, also involve multiple interpretation errors.

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