CVE-2026-21876
Last modified
CVE-2026-21876 is a medium-severity vulnerability rated 5.3/10 on the CVSS scale. 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. EPSS estimates a 13.12% chance of exploitation in the next 30 days.
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/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
Weakness Enumeration
Affected Software
| Vendor | Product | Versions |
|---|---|---|
| Owasp | Owasp Modsecurity Core Rule Set | < 3.3.8 |
| Owasp | Owasp Modsecurity Core Rule Set | >= 4.0.0, < 4.22.0 |
References
- 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
Timeline
- Published
- Last Modified
- Status
- Modified
Frequently Asked Questions
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