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.

The remote Debian 11 host has a package installed that is affected by multiple vulnerabilities as referenced in the dla-4488 advisory.

    -------------------------------------------------------------------------     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
    -------------------------------------------------------------------------

    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     Attachment:
    signature.asc     Description: PGP signature

Tenable has extracted the preceding description block directly from the Debian security advisory.

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

It is, therefore, affected by a vulnerability as referenced in the ALAS2023-2026-1399 advisory.

    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)

Tenable has extracted the preceding description block directly from the tested product security advisory.

Note that Nessus has not tested for this issue but has instead relied only on the application's self-reported version number.

The remote Debian 12 / 13 host has a package installed that is affected by a vulnerability as referenced in the dsa-6105 advisory.

    - -------------------------------------------------------------------------     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
    - -------------------------------------------------------------------------

    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/

    Mailing list: debian-security-announce@lists.debian.org

Tenable has extracted the preceding description block directly from the Debian security advisory.

Note that Nessus has not tested for this issue but has instead relied only on the application's self-reported version number.

The Linux/Unix host has one or more packages installed that are impacted by a vulnerability without a vendor supplied patch available.

  - 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)

Note that Nessus relies on the presence of the package as reported by the vendor.

ID	Name	Product	Family	Severity
299744	Debian dla-4488 : modsecurity-crs - security update	Nessus	Debian Local Security Checks	critical
298074	Amazon Linux 2023 : mod_security_crs (ALAS2023-2026-1399)	Nessus	Amazon Linux Local Security Checks	critical
294903	Debian dsa-6105 : modsecurity-crs - security update	Nessus	Debian Local Security Checks	critical
282487	Linux Distros Unpatched Vulnerability : CVE-2026-21876	Nessus	Misc.	critical

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