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NVD
9.3 CriticalCWE-794
CVE-2026-21876

coreruleset vulnerability

coreruleset

Status
  • Not in CISA KEV
  • Vendor fix available
Exploit probabilityEPSSchecked 25 Oct
18%probability of exploitation in the next 30 days

Higher than 97% of scored CVEs

SeverityCVSS
9.3Critical

Description NVD

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.

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