Essential Guide: CVE-2026-21876 - OWASP CRS has multipart bypass using multiple content-type parts

CVE ID : CVE-2026-21876 Published : Jan. 8, 2026, 2:15 p.m. | 36 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: 9.3 | CRITICAL Visit the link for more details, such as CVSS details, affected products, timeline, and more...

Source: Telegram CVE Monitor