Use After Free in WebSocket server implementation in lws_handshake_server in warmcat libwebsockets may allow an attacker, in specific configurations where the user provides a callback function that handles LWS_CALLBACK_HTTP_CONFIRM_UPGRADE, to achieve denial of service.

The remote Ubuntu 20.04 LTS / 22.04 LTS / 24.04 LTS host has packages installed that are affected by multiple vulnerabilities as referenced in the USN-8024-1 advisory.

    Raffaele Bova discovered that Libwebsockets incorrectly handled memory when the upgrade header is not     valid in the WebSocket server. An attacker could possibly use this issue to cause a denial of service.
    (CVE-2025-11677)

    Raffaele Bova discovered that Libwebsockets did not properly check the size of the destination buffer in     the async-dns component. An attacker could possibly use this issue to cause applications to crash, leading     to a denial of service, or possibly execute arbitrary code. This issue only affected Ubuntu 22.04 LTS and     Ubuntu 24.04 LTS. (CVE-2025-11678)

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

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

According to the versions of the libwebsockets package installed, the EulerOS installation on the remote host is affected by the following vulnerabilities :

    Use After Free in WebSocket server implementation in lws_handshake_server in warmcat libwebsockets may     allow an attacker, in specific configurations where the user provides a callback function that     handlesLWS_CALLBACK_HTTP_CONFIRM_UPGRADE, to achieve denial of service.(CVE-2025-11677)

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

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

According to the versions of the libwebsockets package installed, the EulerOS installation on the remote host is affected by the following vulnerabilities :

    A vulnerability, which was classified as critical, was found in warmcat libwebsockets up to 4.3.6/4.4.2.
    This affects the function lws_handshake_server. There is no information about possible countermeasures     known. It may be suggested to replace the affected object with an alternative product.(CVE-2025-11677)

Tenable has extracted the preceding description block directly from the EulerOS libwebsockets 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 42 host has a package installed that is affected by multiple vulnerabilities as referenced in the FEDORA-2025-0c12fa2541 advisory.

    Update to 4.3.7, enable glib event loop


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

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

The Unity Linux 20 host has a package installed that is affected by a vulnerability as referenced in the UTSA-2025-991026 advisory.

    Use After Free in WebSocket server implementation in lws_handshake_server in warmcat libwebsockets may     allow an attacker, in specific configurations where the user provides a callback function that     handlesLWS_CALLBACK_HTTP_CONFIRM_UPGRADE, to achieve denial of service.

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 Debian 11 host has packages installed that are affected by multiple vulnerabilities as referenced in the dla-4373 advisory.

    - -----------------------------------------------------------------------     Debian LTS Advisory DLA-4373-1              debian-lts@lists.debian.org     https://www.debian.org/lts/security/                      Utkarsh Gupta     November 17, 2025                           https://wiki.debian.org/LTS
    - -----------------------------------------------------------------------

    Package        : libwebsockets     Version        : 4.0.20-2+deb11u1     CVE ID         : CVE-2025-11677 CVE-2025-11678     Debian Bug     : 1118746 1118747

    Libwebsockets (LWS) is a flexible, lightweight pure C library for     implementing modern network protocols easily with a tiny footprint,     using a nonblocking event loop.

    CVE-2025-11677

        Use After Free in WebSocket server implementation in         lws_handshake_server in warmcat libwebsockets may allow an attacker,         in specific configurations where the user provides a callback         function that handles LWS_CALLBACK_HTTP_CONFIRM_UPGRADE, to achieve         denial of service.

    CVE-2025-11678

        Stack-based Buffer Overflow in lws_adns_parse_label in warmcat         libwebsockets allows, when the LWS_WITH_SYS_ASYNC_DNS flag is         enabled during compilation, to overflow the label_stack, when the         attacker is able to sniff a DNS request in order to craft a response         with a matching ID containing a label longer than the maximum.

    For Debian 11 bullseye, these problems have been fixed in version     4.0.20-2+deb11u1.

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

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.

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

  - Use After Free in WebSocket server implementation in lws_handshake_server in warmcat libwebsockets may     allow an attacker, in specific configurations where the user provides a callback function that handles     LWS_CALLBACK_HTTP_CONFIRM_UPGRADE, to achieve denial of service. (CVE-2025-11677)

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

ID	Name	Product	Family	Severity
298804	Ubuntu 20.04 LTS / 22.04 LTS / 24.04 LTS : Libwebsockets vulnerabilities (USN-8024-1)	Nessus	Ubuntu Local Security Checks	high
284759	EulerOS 2.0 SP12 : libwebsockets (EulerOS-SA-2026-1094)	Nessus	Huawei Local Security Checks	medium
284736	EulerOS 2.0 SP12 : libwebsockets (EulerOS-SA-2026-1074)	Nessus	Huawei Local Security Checks	medium
278464	EulerOS 2.0 SP13 : libwebsockets (EulerOS-SA-2025-2504)	Nessus	Huawei Local Security Checks	medium
278421	EulerOS 2.0 SP13 : libwebsockets (EulerOS-SA-2025-2525)	Nessus	Huawei Local Security Checks	medium
278026	Fedora 42 : libwebsockets (2025-0c12fa2541)	Nessus	Fedora Local Security Checks	high
276989	Unity Linux 20.1050e / 20.1060e / 20.1070e Security Update: libwebsockets (UTSA-2025-991026)	Nessus	Unity Linux Local Security Checks	medium
275575	Debian dla-4373 : libwebsockets-dev - security update	Nessus	Debian Local Security Checks	high
271651	Linux Distros Unpatched Vulnerability : CVE-2025-11677	Nessus	Misc.	medium

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