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.
Metrics
CVSS 3.1 5.3/10
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:NWeakness enumeration
Affected software
| Vendor | Product | Versions |
|---|---|---|
| coreruleset | coreruleset | < 4.22.0; < 3.3.8 |
References
- https://github.com/coreruleset/coreruleset/commit/80d80473abf71bd49bf6d3c1ab221e3c74e4eb83Patch
- https://github.com/coreruleset/coreruleset/commit/9917985de09a6cf38b3261faf9105e909d67a7d6Patch
- https://github.com/coreruleset/coreruleset/releases/tag/v3.3.8Product, Release Notes
- https://github.com/coreruleset/coreruleset/releases/tag/v4.22.0Product, Release Notes
- https://github.com/coreruleset/coreruleset/security/advisories/GHSA-36fv-25j3-r2c5Exploit, Vendor Advisory
- https://github.com/daytriftnewgen/CVE-2026-21876
Timeline
- Published
- Jan 8, 2026
- Last modified
- Jun 17, 2026
- NVD status
- Modified