CVE-2026-21876

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 v3 9.3 CRITICAL

9.3^/10

CVSS v3 : CRITICAL

Vector :

Exploitability : 3.9 / Impact : 4.7

Attack Vector NETWORK

Attack Complexity LOW

Privileges Required NONE

User Interaction NONE

Confidentiality Impact HIGH

Integrity Impact LOW

Availability Impact NONE

Scope CHANGED

References

Link	Resource
https://github.com/coreruleset/coreruleset/commit/80d80473abf71bd49bf6d3c1ab221e3c74e4eb83	Patch
https://github.com/coreruleset/coreruleset/commit/9917985de09a6cf38b3261faf9105e909d67a7d6	Patch
https://github.com/coreruleset/coreruleset/releases/tag/v3.3.8	Product Release Notes
https://github.com/coreruleset/coreruleset/releases/tag/v4.22.0	Product Release Notes
https://github.com/coreruleset/coreruleset/security/advisories/GHSA-36fv-25j3-r2c5	Vendor Advisory Exploit

Configurations

Configuration 1 (hide)

OR	cpe:2.3:a:owasp:owasp_modsecurity_core_rule_set::::::::
	cpe:2.3:a:owasp:owasp_modsecurity_core_rule_set::::::::

History

No history.

Information

Published : 2026-01-08 14:15

Updated : 2026-02-23 18:33

NVD link : CVE-2026-21876

Mitre link : CVE-2026-21876

CVE.ORG link : CVE-2026-21876

JSON object : View

Products Affected

owasp

owasp_modsecurity_core_rule_set

CWE

CWE-794

Incomplete Filtering of Multiple Instances of Special Elements

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