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CVE-2026-21876

OWASP CRS has multipart bypass using multiple content-type parts

Published: Jan 8, 2026Updated: Feb 23, 2026 Sources: CVE List NVDCWE-794
NVD MITRE
9.3CVSSCRITICAL
EPSS Score
13.1%
Top 4.1%
CISA KEV
Not in KEV
Exploits
No Known Exploits
Remediation
Patch Available

Description

The OWASP core rule set (CRS) is a set of generic attack detection rules for use with compatible web application firewalls. Prior to versions 4.22.0 and 3.3.8, the current rule 922110 has a bug when processing multipart requests with multiple parts. When the first rule in a chain iterates over a collection (like `MULTIPART_PART_HEADERS`), the capture variables (`TX:0`, `TX:1`) get overwritten with each iteration. Only the last captured value is available to the chained rule, which means malicious charsets in earlier parts can be missed if a later part has a legitimate charset. Versions 4.22.0 and 3.3.8 patch the issue.

CVSS Vector Breakdown

AV:NAC:LPR:NUI:NS:CC:HI:LA:N
Exploitability
AV:NAttack Vector
Network
AC:LAttack Complexity
Low
PR:NPrivileges Required
None
UI:NUser Interaction
None
Scope
S:CScope
Changed
Impact
C:HConfidentiality
High
I:LIntegrity
Low
A:NAvailability
None
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Weaknesses

CWE-794

Affected Products

corerulesetcoreruleset
Mixed
Networking Infrastructure / firewall
owasp modsecurity core rule setowasp
Mixed
Networking Infrastructure / firewall
corerulesetoss-projectNetworking Infrastructureaka coreruleset (owasp modsecurity core rule set)
owasposs-projectUSNetworking Infrastructureaka owasp modsecurity core rule set, modsecurity, modsecurity-crs

Exploitability

Official Patch Available

References

https://github.com/coreruleset/coreruleset/security/advisories/GHSA-36fv-25j3-r2c5
github.com
https://github.com/coreruleset/coreruleset/commit/80d80473abf71bd49bf6d3c1ab221e3c74e4eb83
github.com
https://github.com/coreruleset/coreruleset/commit/9917985de09a6cf38b3261faf9105e909d67a7d6
github.com
and 2 more references View all →

Timeline

Published
Jan 8, 2026
Last Updated
Feb 23, 2026

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