Owasp Modsecurity Core Rule Set
CVE-2026-21876
CRITICAL
Severity by source
AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:L/A:N
Primary rating from GitHub Advisory · only source for this CVE.
CVSS VectorGitHub Advisory
Lifecycle Timeline
4DescriptionGitHub Advisory
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.
AnalysisAI
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. PoC available, patch available.
Technical ContextAI
When rule 922110 processes multipart requests with multiple parts (CWE-794), the capture variables (TX:0, TX:1) from the first rule in a chain get overwritten by subsequent parts. This means the rule fails to detect attack patterns that span across or are hidden within multiple multipart parts.
RemediationAI
Update CRS to 4.22.0 or 3.3.8. Review WAF logs for multipart-based attacks that may have bypassed detection.
OWASP ModSecurity Core Rule Set 3.1.x before 3.1.2, 3.2.x before 3.2.1, and 3.3.x before 3.3.2 is affected by a Request
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The OWASP ModSecurity Core Rule Set (CRS) is affected by a partial rule set bypass for HTTP multipart requests by submit
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An issue was discovered in OWASP ModSecurity Core Rule Set (CRS) through 3.1.0. Rated medium severity (CVSS 5.3), this v
An issue was discovered in OWASP ModSecurity Core Rule Set (CRS) through 3.1.0. Rated medium severity (CVSS 5.3), this v
An issue was discovered in OWASP ModSecurity Core Rule Set (CRS) through 3.1.0. Rated medium severity (CVSS 5.3), this v
An issue was discovered in OWASP ModSecurity Core Rule Set (CRS) through 3.1.0. Rated medium severity (CVSS 5.3), this v
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The OWASP ModSecurity Core Rule Set (CRS) is affected by a response body bypass. Rated high severity (CVSS 7.5), this vu
An issue was discovered in OWASP ModSecurity Core Rule Set (CRS) through 3.1.0. Rated medium severity (CVSS 5.3), this v
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