warmcat libwebsockets up to 4.3.6/4.4.2 lws_handshake_server use after free

Summaryinfo

A vulnerability, which was classified as critical, has been found in warmcat libwebsockets up to 4.3.6/4.4.2. Affected by this vulnerability is the function lws_handshake_server. Performing a manipulation results in use after free. This vulnerability was named CVE-2025-11677. The attack may be initiated remotely. There is no available exploit.

Detailsinfo

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. The manipulation with an unknown input leads to a use after free vulnerability. CWE is classifying the issue as CWE-416. Referencing memory after it has been freed can cause a program to crash, use unexpected values, or execute code. This is going to have an impact on confidentiality, integrity, and availability. The summary by CVE is:

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 weakness was presented by Raffaele Bova. It is possible to read the advisory at libwebsockets.org. This vulnerability is uniquely identified as CVE-2025-11677 since 10/13/2025. The exploitability is told to be difficult. It is possible to initiate the attack remotely. No form of authentication is needed for exploitation. Technical details of the vulnerability are known, but there is no available exploit. The pricing for an exploit might be around USD $0-$5k at the moment (estimation calculated on 10/28/2025).

The vulnerability scanner Nessus provides a plugin with the ID 271651 (Linux Distros Unpatched Vulnerability : CVE-2025-11677), which helps to determine the existence of the flaw in a target environment.

There is no information about possible countermeasures known. It may be suggested to replace the affected object with an alternative product.

The vulnerability is also documented in the databases at Tenable (271651) and EUVD (EUVD-2025-35045). Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.

Productinfo

Vendor

• warmcat

Name

• libwebsockets

Version

• 4.3.0
• 4.3.1
• 4.3.2
• 4.3.3
• 4.3.4
• 4.3.5
• 4.3.6
• 4.4.0
• 4.4.1
• 4.4.2

CPE 2.3info

• 🔒
• 🔒
• 🔒

CPE 2.2info

• 🔒
• 🔒
• 🔒

CVSSv4info

CVSSv3info

CVSSv2info

Exploitinginfo

Threat Intelligenceinfo

Countermeasuresinfo

Timelineinfo

Sourcesinfo

Entryinfo

Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.

Discussion