Common Weakness Enumeration

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CWE-436: Interpretation Conflict

Weakness ID: 436
Abstraction: Base
Structure: Simple
Status: Incomplete
Presentation Filter:
+ 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.
+ Relationships

The table(s) below shows the weaknesses and high level categories that are related to this weakness. These relationships are defined as ChildOf, ParentOf, MemberOf and give insight to similar items that may exist at higher and lower levels of abstraction. In addition, relationships such as PeerOf and CanAlsoBe are defined to show similar weaknesses that the user may want to explore.

+ Relevant to the view "Weaknesses for Simplified Mapping of Published Vulnerabilities" (CWE-1003)
+ Relevant to the view "Development Concepts" (CWE-699)
+ Modes Of Introduction

The different Modes of Introduction provide information about how and when this weakness may be introduced. The Phase identifies a point in the software life cycle at which introduction may occur, while the Note provides a typical scenario related to introduction during the given phase.

Architecture and Design
+ Applicable Platforms
The listings below show possible areas for which the given weakness could appear. These may be for specific named Languages, Operating Systems, Architectures, Paradigms, Technologies, or a class of such platforms. The platform is listed along with how frequently the given weakness appears for that instance.


Class: Language-Independent (Undetermined Prevalence)

+ Common Consequences

The table below specifies different individual consequences associated with the weakness. The Scope identifies the application security area that is violated, while the Impact describes the negative technical impact that arises if an adversary succeeds in exploiting this weakness. The Likelihood provides information about how likely the specific consequence is expected to be seen relative to the other consequences in the list. For example, there may be high likelihood that a weakness will be exploited to achieve a certain impact, but a low likelihood that it will be exploited to achieve a different impact.


Technical Impact: Unexpected State; Varies by Context

+ Demonstrative Examples

Example 1

The paper "Insertion, Evasion, and Denial of Service: Eluding Network Intrusion Detection" [REF-428] shows that OSes varied widely in how they manage unusual packets, which made it difficult or impossible for intrusion detection systems to properly detect certain attacker manipulations that took advantage of these OS differences.

Example 2

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 [REF-429] and PHP.

+ Observed Examples
Bypass filters or poison web cache using requests with multiple Content-Length headers, a non-standard behavior.
Anti-virus product allows bypass via Content-Type and Content-Disposition headers that are mixed case, which are still processed by some clients.
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.
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.
Virus product bypass with spaces between MIME header fields and the ":" separator, a non-standard message that is accepted by some clients.
AV product detection bypass using inconsistency manipulation (file extension in MIME Content-Type vs. Content-Disposition field).
CMS system allows uploads of files with GIF/JPG extensions, but if they contain HTML, Internet Explorer renders them as HTML instead of images.
Interpretation conflict allows XSS via invalid "<" when a ">" is expected, which is treated as ">" by many web browsers.
Interpretation conflict (non-standard behavior) enables XSS because browser ignores invalid characters in the middle of tags.
+ Memberships
This MemberOf Relationships table shows additional CWE Categories and Views that reference this weakness as a member. This information is often useful in understanding where a weakness fits within the context of external information sources.
MemberOfCategoryCategory957SFP Secondary Cluster: Protocol Error
+ Taxonomy Mappings
Mapped Taxonomy NameNode IDFitMapped Node Name
PLOVERMultiple Interpretation Error (MIE)
WASC27HTTP Response Smuggling
+ References
[REF-427] Steve Christey. "On Interpretation Conflict Vulnerabilities". Bugtraq. 2005-11-03.
[REF-428] Thomas H. Ptacek and Timothy N. Newsham. "Insertion, Evasion, and Denial of Service: Eluding Network Intrusion Detection". 1998-01. <>.
[REF-429] Brett Moore. "0x00 vs ASP file upload scripts". 2004-07-13. <>.
[REF-430] Rain Forest Puppy. "Poison NULL byte". Phrack.
[REF-431] David F. Skoll. "Re: Corsaire Security Advisory - Multiple vendor MIME RFC2047 encoding". Bugtraq. 2004-09-15. <>.
+ Content History
Submission DateSubmitterOrganization
Modification DateModifierOrganization
2008-07-01Eric DalciCigital
updated Time_of_Introduction
2008-09-08CWE Content TeamMITRE
updated Relationships, Other_Notes, Taxonomy_Mappings
2008-10-14CWE Content TeamMITRE
updated Description
2009-05-27CWE Content TeamMITRE
updated Related_Attack_Patterns
2009-10-29CWE Content TeamMITRE
updated Relationships
2010-02-16CWE Content TeamMITRE
updated Relationships, Taxonomy_Mappings
2010-04-05CWE Content TeamMITRE
updated Related_Attack_Patterns
2011-06-01CWE Content TeamMITRE
updated Common_Consequences
2011-06-27CWE Content TeamMITRE
updated Common_Consequences
2012-05-11CWE Content TeamMITRE
updated Relationships
2014-06-23CWE Content TeamMITRE
updated Applicable_Platforms, Description, Observed_Examples, Other_Notes, References
2014-07-30CWE Content TeamMITRE
updated Relationships
2015-12-07CWE Content TeamMITRE
updated Relationships
2017-01-19CWE Content TeamMITRE
updated Relationships
2017-11-08CWE Content TeamMITRE
updated Demonstrative_Examples, Observed_Examples, References, Relationships
Previous Entry Names
Change DatePrevious Entry Name
2008-04-11Multiple Interpretation Error (MIE)

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Page Last Updated: January 18, 2018