CVE-2026-21876
CRITICALCVSS Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:L/A:N
Lifecycle Timeline
4Description
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.
Analysis
OWASP Core Rule Set (CRS) before 4.22.0 and 3.3.8 has a bug in rule 922110 that allows WAF bypass on multipart requests. The rule's capture variables get overwritten when processing multiple parts, allowing SQL injection and other attacks to slip through. …
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Remediation
Within 24 hours: Identify all affected systems and apply vendor patches immediately. Vendor patch is available.
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