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CVE-2026-21876
Good to know:
Date: January 8, 2026
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.
Severity Score
Related Resources (7)
Severity Score
Weakness Type (CWE)
Incomplete Filtering of Multiple Instances of Special Elements
CWE-794Top Fix
Upgrade Version
Upgrade to version https://github.com/coreruleset/coreruleset.git - v4.22.0;https://github.com/coreruleset/coreruleset.git - v3.3.8
CVSS v3.1
| Base Score: |
|
|---|---|
| Attack Vector (AV): | NETWORK |
| Attack Complexity (AC): | LOW |
| Privileges Required (PR): | NONE |
| User Interaction (UI): | NONE |
| Scope (S): | CHANGED |
| Confidentiality (C): | HIGH |
| Integrity (I): | LOW |
| Availability (A): | NONE |