CVE-2026-21876 – OWASP CRS has multipart bypass using multiple content-type parts

CVE ID : CVE-2026-21876

Published : Jan. 8, 2026, 1:55 p.m. | 32 minutes ago

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.

Severity: 0.0 | NA

Visit the link for more details, such as CVSS details, affected products, timeline, and more…