Debian alert DLA-4488-1 (modsecurity-crs)

From:
             
 
Tobias Frost <tobi@debian.org>
To:
             
 
debian-lts-announce@lists.debian.org
Subject:
             
 
[SECURITY] [DLA 4488-1] modsecurity-crs security update
Date:
             
 
Sun, 22 Feb 2026 11:03:27 +0100
Message-ID:
             
 
<aZrUb9ihJx3_uoF2@isildor2.loewenhoehle.ip>
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Debian LTS Advisory DLA-4488-1                debian-lts@lists.debian.org
https://www.debian.org/lts/security/                         Tobias Frost
February 22, 2026                             https://wiki.debian.org/LTS
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Package        : modsecurity-crs
Version        : 3.3.4-1~deb11u2
CVE ID         : CVE-2023-38199 CVE-2026-21876
Debian Bug     : 1041109 1125084

Multiple issues have been fixed in modsecurity-crs, a set of generic 
attack detection rules for use with ModSecurity.

CVE-2023-38199

    Coreruleset (aka OWASP ModSecurity Core Rule Set) through 3.3.4 does not
    detect multiple Content-Type request headers on some platforms. This
    might allow attackers to bypass a WAF with a crafted payload, aka
    "Content-Type confusion" between the WAF and the backend application.
    This occurs when the web application relies on only the last
    Content-Type header. Other platforms may reject the additional
    Content-Type header or merge conflicting headers, leading to detection
    as a malformed header.

CVE-2026-21876

    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.

For Debian 11 bullseye, these problems have been fixed in version
3.3.4-1~deb11u2.

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 LTS security advisories, how to apply
these updates to your system and frequently asked questions can be
found at: https://wiki.debian.org/LTS


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