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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History
Thu, 08 Jan 2026 18:15:00 +0000
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Thu, 08 Jan 2026 14:15:00 +0000
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| Description | 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. | |
| Title | OWASP CRS has multipart bypass using multiple content-type parts | |
| Weaknesses | CWE-794 | |
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cvssV3_1
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Status: PUBLISHED
Assigner: GitHub_M
Published:
Updated: 2026-01-08T15:55:33.073Z
Reserved: 2026-01-05T17:24:36.927Z
Link: CVE-2026-21876
Updated: 2026-01-08T14:52:52.629Z
Status : Awaiting Analysis
Published: 2026-01-08T14:15:57.087
Modified: 2026-01-08T18:08:18.457
Link: CVE-2026-21876
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OpenCVE Enrichment
No data.