# CVE-2025-11677: libwebsockets-evlib-ev: Use After Free in WebSocket server implementation in lws_handshake_server in warmcat libwebsockets may allow an attac...

CVE-2025-11677 is fixed in 9 products on 1 platform, first by libwebsockets-evlib-ev 4.3.3-1.1ubuntu0.1~esm1, released October 20, 2025. It is not reported as exploited. Patch Radar priority: Routine.

- Web page: https://patchblox.com/security/cve/CVE-2025-11677
- Priority: Routine
- CVSS: n/a (Medium)
- EPSS: 0.0041
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Oct 20, 2025

## 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.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | libwebsockets Debian 11.6 (bullseye) | 4.0.20-2+deb11u1 | [DLA-4373-1](https://patchblox.com/security/data/fix/linux/dla-4373-1.md) | Nov 17, 2025 |
| Linux | libwebsockets Debian 13.5 (trixie) | 4.3.5-1+deb13u1 | [DEBIAN-CVE-2025-11677](https://patchblox.com/security/data/fix/linux/debian-cve-2025-11677.md) | Oct 20, 2025 |
| Linux | libwebsockets Debian 14 | 4.3.5-3 | [DEBIAN-CVE-2025-11677](https://patchblox.com/security/data/fix/linux/debian-cve-2025-11677.md) | Oct 20, 2025 |
| Linux | libwebsockets-evlib-ev Ubuntu 24.04.5 LTS (noble) | 4.3.3-1.1ubuntu0.1~esm1 | [libwebsockets-evlib-ev 4.3.3-1.1ubuntu0.1~esm1](https://patchblox.com/security/data/fix/linux/ubuntu-noble-libwebsockets-evlib-ev-4.3.3-1.1ubuntu0.1-esm1.md) | Oct 20, 2025 |
| Linux | libwebsockets-evlib-glib Ubuntu 24.04.5 LTS (noble) | 4.3.3-1.1ubuntu0.1~esm1 | [libwebsockets-evlib-glib 4.3.3-1.1ubuntu0.1~esm1](https://patchblox.com/security/data/fix/linux/ubuntu-noble-libwebsockets-evlib-glib-4.3.3-1.1ubuntu0.1-esm1.md) | Oct 20, 2025 |
| Linux | libwebsockets-evlib-uv Ubuntu 24.04.5 LTS (noble) | 4.3.3-1.1ubuntu0.1~esm1 | [libwebsockets-evlib-uv 4.3.3-1.1ubuntu0.1~esm1](https://patchblox.com/security/data/fix/linux/ubuntu-noble-libwebsockets-evlib-uv-4.3.3-1.1ubuntu0.1-esm1.md) | Oct 20, 2025 |
| Linux | libwebsockets-test-server Ubuntu 20.04 LTS (focal) | 3.2.1-3ubuntu0.1~esm1 | [libwebsockets-test-server 3.2.1-3ubuntu0.1~esm1](https://patchblox.com/security/data/fix/linux/ubuntu-focal-libwebsockets-test-server-3.2.1-3ubuntu0.1-esm1.md) | Oct 20, 2025 |
| Linux | libwebsockets-test-server Ubuntu 22.04.1 LTS (jammy) | 4.0.20-2ubuntu1.1 | [libwebsockets-test-server 4.0.20-2ubuntu1.1](https://patchblox.com/security/data/fix/linux/ubuntu-jammy-libwebsockets-test-server-4.0.20-2ubuntu1.1.md) | Oct 20, 2025 |
| Linux | libwebsockets-test-server Ubuntu 24.04.5 LTS (noble) | 4.3.3-1.1ubuntu0.1~esm1 | [libwebsockets-test-server 4.3.3-1.1ubuntu0.1~esm1](https://patchblox.com/security/data/fix/linux/ubuntu-noble-libwebsockets-test-server-4.3.3-1.1ubuntu0.1-esm1.md) | Oct 20, 2025 |
| Linux | libwebsockets-test-server-common Ubuntu 20.04 LTS (focal) | 3.2.1-3ubuntu0.1~esm1 | [libwebsockets-test-server-common 3.2.1-3ubuntu0.1~esm1](https://patchblox.com/security/data/fix/linux/ubuntu-focal-libwebsockets-test-server-common-3.2.1-3ubuntu0.1-esm1.md) | Oct 20, 2025 |
| Linux | libwebsockets-test-server-common Ubuntu 22.04.1 LTS (jammy) | 4.0.20-2ubuntu1.1 | [libwebsockets-test-server-common 4.0.20-2ubuntu1.1](https://patchblox.com/security/data/fix/linux/ubuntu-jammy-libwebsockets-test-server-common-4.0.20-2ubuntu1.1.md) | Oct 20, 2025 |
| Linux | libwebsockets-test-server-common Ubuntu 24.04.5 LTS (noble) | 4.3.3-1.1ubuntu0.1~esm1 | [libwebsockets-test-server-common 4.3.3-1.1ubuntu0.1~esm1](https://patchblox.com/security/data/fix/linux/ubuntu-noble-libwebsockets-test-server-common-4.3.3-1.1ubuntu0.1-esm1.md) | Oct 20, 2025 |
| Linux | libwebsockets15 Ubuntu 20.04 LTS (focal) | 3.2.1-3ubuntu0.1~esm1 | [libwebsockets15 3.2.1-3ubuntu0.1~esm1](https://patchblox.com/security/data/fix/linux/ubuntu-focal-libwebsockets15-3.2.1-3ubuntu0.1-esm1.md) | Oct 20, 2025 |
| Linux | libwebsockets16 Ubuntu 22.04.1 LTS (jammy) | 4.0.20-2ubuntu1.1 | [libwebsockets16 4.0.20-2ubuntu1.1](https://patchblox.com/security/data/fix/linux/ubuntu-jammy-libwebsockets16-4.0.20-2ubuntu1.1.md) | Oct 20, 2025 |
| Linux | libwebsockets19t64 Ubuntu 24.04.5 LTS (noble) | 4.3.3-1.1ubuntu0.1~esm1 | [libwebsockets19t64 4.3.3-1.1ubuntu0.1~esm1](https://patchblox.com/security/data/fix/linux/ubuntu-noble-libwebsockets19t64-4.3.3-1.1ubuntu0.1-esm1.md) | Oct 20, 2025 |

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Data as of 2026-11-09T01:18:40Z UTC. Source: Patchblox Patch Radar (https://patchblox.com/security/patch-radar). Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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