Amazon Linux 2023 Security Advisory: ALAS2023-2026-1399
Advisory Released Date: 2026-02-05
Advisory Updated Date: 2026-02-05
Severity:
Important
Issue Overview:
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. (CVE-2026-21876)
Affected Packages:
mod_security_crs
Issue Correction:
Run dnf update mod_security_crs --releasever 2023.10.20260202 or dnf update --advisory ALAS2023-2026-1399 --releasever 2023.10.20260202 to update your system.
More information on how to update your system can be found on this page: Amazon Linux 2023 documentation
New Packages:
noarch:
mod_security_crs-4.2.0-1.amzn2023.0.2.noarch
src:
mod_security_crs-4.2.0-1.amzn2023.0.2.src