libwebsockets HTTP/2 HPACK Path Header Parsing Out-Of-Bounds Write Remote Code Execution Vulnerability. This vulnerability allows remote attackers to execute arbitrary code on affected installations of libwebsockets. Authentication is not required to exploit this vulnerability. The specific flaw exists within the parsing of HTTP/2 HPACK path header. The issue results from the lack of proper validation of user-supplied data, which can result in a write past the end of an allocated buffer. An attacker can leverage this vulnerability to execute code in the context of the current process. Was ZDI-CAN-31036.

The Unity Linux 20 host has a package installed that is affected by a vulnerability as referenced in the UTSA-2026-142308 advisory.

    libwebsockets HTTP/2 HPACK Path Header Parsing Out-Of-Bounds Write Remote Code Execution Vulnerability.
    This vulnerability allows remote attackers to execute arbitrary code on affected installations of     libwebsockets. Authentication is not required to exploit this vulnerability.

    The specific flaw exists within the parsing of HTTP/2 HPACK path header. The issue results from the lack     of proper validation of user-supplied data, which can result in a write past the end of an allocated     buffer. An attacker can leverage this vulnerability to execute code in the context of the current process.
    Was ZDI-CAN-31036.

Tenable has extracted the preceding description block directly from the Unity Linux 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 Ubuntu 16.04 LTS / 18.04 LTS / 20.04 LTS / 22.04 LTS / 24.04 LTS / 26.04 LTS host has packages installed that are affected by a vulnerability as referenced in the USN-8893-1 advisory.

    It was discovered that libwebsockets did not properly validate user-supplied data when parsing HTTP/2     HPACK path headers, which could result in a write past the end of an allocated buffer. An attacker could     possibly use this issue to execute arbitrary code. (CVE-2026-19773)

    It was discovered that libwebsockets did not properly handle CBOR recording in the LECP parser, which     could result in a write past the end of an allocated buffer. An attacker could possibly use this issue to     cause a crash or execute arbitrary code. (CVE-2026-78161)

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 Debian 13 host has packages installed that are affected by a vulnerability as referenced in the dsa-6529 advisory.

    - -------------------------------------------------------------------------     Debian Security Advisory DSA-6529-1                   security@debian.org     https://www.debian.org/security/                       Moritz Muehlenhoff     September 29, 2026                    https://www.debian.org/security/faq
    - -------------------------------------------------------------------------

    Package        : libwebsockets     CVE ID         : CVE-2026-19773

    It was discovered that missing input validation in the hpack path     header parser of libwebsockets could result in denial of service or     potentially the execution of arbitrary code.

    For the stable distribution (trixie), this problem has been fixed in     version 4.3.5-1+deb13u3.

    We recommend that you upgrade your libwebsockets packages.

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

    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.

  - libwebsockets HTTP/2 HPACK Path Header Parsing Out-Of-Bounds Write Remote Code Execution Vulnerability.
    This vulnerability allows remote attackers to execute arbitrary code on affected installations of     libwebsockets. Authentication is not required to exploit this vulnerability. The specific flaw exists     within the parsing of HTTP/2 HPACK path header. The issue results from the lack of proper validation of     user-supplied data, which can result in a write past the end of an allocated buffer. An attacker can     leverage this vulnerability to execute code in the context of the current process. Was ZDI-CAN-31036.
    (CVE-2026-19773)

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

ID	Name	Product	Family	Type	Severity
370120	Unity Linux 20.1050e / 20.1060e / 20.1070e Security Update: libwebsockets (UTSA-2026-142308)	Nessus	Unity Linux Local Security Checks	Local	critical
364280	Ubuntu 16.04 LTS / 18.04 LTS / 20.04 LTS / 22.04 LTS / 24.04 LTS / 26.04 LTS : Libwebsockets vulnerabilities (USN-8893-1)	Nessus	Ubuntu Local Security Checks	Local	critical
351210	Debian dsa-6529 : libwebsockets-dev - security update	Nessus	Debian Local Security Checks	Local	critical
346356	Linux Distros Unpatched Vulnerability : CVE-2026-19773	Nessus	Misc.	Local	critical

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