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.

Primary

Architecture and Design

Implementation

Integrity
Other
Unexpected State
Varies by Context

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.

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.

CVE-2005-1215
Bypass filters or poison web cache using requests with multiple Content-Length headers, a non-standard behavior.
https://www.cve.org/CVERecord?id=CVE-2005-1215

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.
https://www.cve.org/CVERecord?id=CVE-2002-0485

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.
https://www.cve.org/CVERecord?id=CVE-2002-1978

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.
https://www.cve.org/CVERecord?id=CVE-2002-1979

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.
https://www.cve.org/CVERecord?id=CVE-2002-0637

CVE-2002-1777
AV product detection bypass using inconsistency manipulation (file extension in MIME Content-Type vs. Content-Disposition field).
https://www.cve.org/CVERecord?id=CVE-2002-1777

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.
https://www.cve.org/CVERecord?id=CVE-2005-3310

CVE-2005-4260
Interpretation conflict allows XSS via invalid "<" when a ">" is expected, which is treated as ">" by many web browsers.
https://www.cve.org/CVERecord?id=CVE-2005-4260

CVE-2005-4080
Interpretation conflict (non-standard behavior) enables XSS because browser ignores invalid characters in the middle of tags.
https://www.cve.org/CVERecord?id=CVE-2005-4080

Multiple Interpretation Error (MIE)

27
HTTP Response Smuggling

Allowed-with-Review
This CWE entry is a Class and might have Base-level children that would be more appropriate
Examine children of this entry to see if there is a better fit

PLOVER
2006-07-19
Draft 3
2006-07-19

Eric Dalci
Cigital
2008-07-01
updated Time_of_Introduction

CWE Content Team
MITRE
2008-09-08
updated Relationships, Other_Notes, Taxonomy_Mappings

CWE Content Team
MITRE
2008-10-14
updated Description

CWE Content Team
MITRE
2009-05-27
updated Related_Attack_Patterns

CWE Content Team
MITRE
2009-10-29
updated Relationships

CWE Content Team
MITRE
2010-02-16
updated Relationships, Taxonomy_Mappings

CWE Content Team
MITRE
2010-04-05
updated Related_Attack_Patterns

CWE Content Team
MITRE
2011-06-01
updated Common_Consequences

CWE Content Team
MITRE
2011-06-27
updated Common_Consequences

CWE Content Team
MITRE
2012-05-11
updated Relationships

CWE Content Team
MITRE
2014-06-23
updated Applicable_Platforms, Description, Observed_Examples, Other_Notes, References

CWE Content Team
MITRE
2014-07-30
updated Relationships

CWE Content Team
MITRE
2015-12-07
updated Relationships

CWE Content Team
MITRE
2017-01-19
updated Relationships

CWE Content Team
MITRE
2017-11-08
updated Demonstrative_Examples, Observed_Examples, References, Relationships

CWE Content Team
MITRE
2018-03-27
updated References

CWE Content Team
MITRE
2019-06-20
updated Relationships, Type

CWE Content Team
MITRE
2020-02-24
updated Relationships

CWE Content Team
MITRE
2020-08-20
updated Related_Attack_Patterns

CWE Content Team
MITRE
2022-04-28
updated Related_Attack_Patterns

CWE Content Team
MITRE
2022-06-28
updated Relationships

CWE Content Team
MITRE
2023-04-27
updated References, Relationships

CWE Content Team
MITRE
2023-06-29
updated Mapping_Notes

CWE Content Team
MITRE
2025-09-09
4.18
2025-09-09
updated References

CWE Content Team
MITRE
2025-12-11
4.19
2025-12-11
updated Applicable_Platforms, Relationships, Weakness_Ordinalities

Multiple Interpretation Error (MIE)