Debian has released a security update for the modsecurity-crs package to address a vulnerability in the OWASP ModSecurity Core Rule Set. The issue occurs when parsing some multipart requests, which can lead to incorrect rule execution. The bug was fixed in version 3.3.4-1+deb12u1 for Debian GNU/Linux 12 (Bookworm) and version 3.3.7-1+deb13u1 for Debian GNU/Linux 13 (Trixie).

[DSA 6105-1] modsecurity-crs security update

[SECURITY] [DSA 6105-1] modsecurity-crs security update

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Debian Security Advisory DSA-6105-1 security@debian.org
https://www.debian.org/security/ Moritz Muehlenhoff
January 21, 2026 https://www.debian.org/security/faq
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Package : modsecurity-crs
CVE ID : CVE-2026-21876

It was discovered that one of the rules in the OWASP ModSecurity Core
Rule Set parsed some multipart requests incorrectly.

For the oldstable distribution (bookworm), this problem has been fixed
in version 3.3.4-1+deb12u1.

For the stable distribution (trixie), this problem has been fixed in
version 3.3.7-1+deb13u1.

We recommend that you upgrade your modsecurity-crs packages.

For the detailed security status of modsecurity-crs please refer to
its security tracker page at:
https://security-tracker.debian.org/tracker/modsecurity-crs

Further information about Debian Security Advisories, how to apply
these updates to your system and frequently asked questions can be
found at: https://www.debian.org/security/