CVE-2026-21876The OWASP core rule set (CRS) is a set of generic attack detection rules for use with compatible web application firewalls.
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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
- 5.3 MEDIUM (v3.1, NVD)CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
- Weakness (CWE)
- CWE-794
- Known exploited
- Not in CISA's KEV catalog
- EPSS (exploitation in the next 30 days)
- Not loaded for this CVE
- Assigned by
- Not given
- NVD analysis
- Modified
- Record last updated
- Jun 17, 2026
- First seen by InfoSec Signals
- Oct 9, 2026
Affected products
owasp owasp_modsecurity_core_rule_set owasp:owasp_modsecurity_core_rule_set | before 3.3.8; from 4.0.0 before 4.22.0 | NVD |
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
The CVE record on cve.org NVD's entry
The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.