multipart is a fast multipart/form-data parser for python. Prior to 1.2.2, 1.3.1 and 1.4.0-dev, the parse_options_header() function in multipart.py uses a regular expression with an ambiguous alternation, which can cause exponential backtracking (ReDoS) when parsing maliciously crafted HTTP or multipart segment headers. This can be abused for denial of service (DoS) attacks against web applications using this library to parse request headers or multipart/form-data streams. The issue is fixed in 1.2.2, 1.3.1 and 1.4.0-dev.

The remote Ubuntu 25.10 / 26.04 LTS host has a package installed that is affected by a vulnerability as referenced in the USN-8343-1 advisory.

    It was discovered that multipart had an ambiguous regular expression alternation when handling certain     HTTP header values. A remote attacker could possibly use this issue to cause multipart to use excessive     resources, leading to a denial of service.

Tenable has extracted the preceding description block directly from the Ubuntu 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 Fedora 43 host has a package installed that is affected by a vulnerability as referenced in the FEDORA-2026-5c75eb75d1 advisory.

    Update to version 1.3.1 to fix CVE-2026-28356.

Tenable has extracted the preceding description block directly from the Fedora 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 13 host has a package installed that is affected by a vulnerability as referenced in the dsa-6161 advisory.

    - -------------------------------------------------------------------------     Debian Security Advisory DSA-6161-1                   security@debian.org     https://www.debian.org/security/                       Moritz Muehlenhoff     March 12, 2026                        https://www.debian.org/security/faq
    - -------------------------------------------------------------------------

    Package        : multipart     CVE ID         : CVE-2026-28356

    It was discovered that the parse_options_header() function of multipart,     a Python multipart/form-data parser was susceptible to denial of service     via malformed request headers or multipart/form-data streams.

    For the stable distribution (trixie), this problem has been fixed in     version 1.2.1-2+deb13u1.

    We recommend that you upgrade your multipart packages.

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

    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.

ID	Name	Product	Family	Severity
318128	Ubuntu 25.10 / 26.04 LTS : multipart vulnerability (USN-8343-1)	Nessus	Ubuntu Local Security Checks	high
303583	Fedora 43 : python-multipart (2026-5c75eb75d1)	Nessus	Fedora Local Security Checks	high
302009	Debian dsa-6161 : python3-multipart - security update	Nessus	Debian Local Security Checks	high

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CVE-2026-28356

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Tenable Plugins

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