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

> A use-after-free flaw in libwebsockets can cause denial of service in specific configurations involving custom HTTP upgrade callbacks.

- **Severity:** Medium 6.3 (`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`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 20 Oct 2025
- **Updated:** 24 Oct 2025
- **Also known as:** BELL-CVE-2025-11677, DEBIAN-CVE-2025-11677, GHSA-fpc8-25p9-jfmr, UBUNTU-CVE-2025-11677

## What is CVE-2025-11677?

CVE-2025-11677 is a medium-severity use after free vulnerability in warmcat libwebsockets, published on 20 Oct 2025. An attacker can exploit it over the internet without logging in, with no action from the victim.

### 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.

Weakness: CWE-416 (Use After Free)

## Which versions are affected by CVE-2025-11677?


## How do I fix CVE-2025-11677?

Apply the vendor's patch.

## Is CVE-2025-11677 being exploited?

There is no known exploitation of CVE-2025-11677 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2025-11677 and fix it if it is affected.

What it is: CVE-2025-11677 is a medium-severity use after free vulnerability in warmcat libwebsockets, published on 20 Oct 2025. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2025-11677 in the wild and no public exploit code.

Affected product: warmcat libwebsockets. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2025-11677/ (Markdown: https://insights.sbomify.com/CVE-2025-11677/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-11677
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-11677
- OSV: https://osv.dev/vulnerability/CVE-2025-11677

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-11677/
Summaries are generated and may contain mistakes; the official description above is the record.