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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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