Vulnerability · Published Oct 20, 2025 · Assigned by Nozomi
CVE-2025-11677Use After Free in libwebsockets WebSocket server
Medium 6.3
In plain English
A medium-severity use-after-free in libwebsockets from warmcat. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.4% (higher than 35% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Severity (CVSS 4.0)6.3Medium
Exploit odds (30 days)0.4%top 65.1% of all CVEs
Exploited in the wildNo reportsCISA SSVC: none
Attack toolingNoneno public tooling known
Official 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 packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian:12 | libwebsockets | no fix listed | DEBIAN-CVE-2025-11677 |
| Debian:13 | libwebsockets | 4.3.5-1+deb13u1 | DEBIAN-CVE-2025-11677 |
| Debian:14 | libwebsockets | 4.3.5-3 | DEBIAN-CVE-2025-11677 |
| Ubuntu:22.04:LTS | libwebsockets | 4.0.20-2ubuntu1.1 | USN-8024-1 |
| Ubuntu:22.04:LTS | libwebsockets | 4.0.20-2ubuntu1.1 | UBUNTU-CVE-2025-11677 |
| Ubuntu:25.10 | libwebsockets | no fix listed | UBUNTU-CVE-2025-11677 |
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| warmcat | libwebsockets | 3 – through 4.4.1,4.3.6 |
Weakness: CWE-416 · Vector: CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N
References
- https://libwebsockets.org/git/libwebsockets/commit?id=2f082ec31261f556969160143ba94875d783971a patch, vendor-advisory
- https://www.nozominetworks.com/labs/vulnerability-advisories-cve-2025-11677 third-party-advisory