What’s Vulnerable › Vulnerabilities

CVE-2025-11677: Use After Free in libwebsockets WebSocket server

• Severity: medium (CVSS 6.3 v4.0)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.4% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2025-10-20 · updated 2026-10-08
• Weakness: CWE-416

Description

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.

Affected products

• warmcat libwebsockets: from 3 through 4.4.1,4.3.6

References

• https://libwebsockets.org/git/libwebsockets/commit?id=2f082ec31261f556969160143ba94875d783971a
• https://www.nozominetworks.com/labs/vulnerability-advisories-cve-2025-11677

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