# CVE-2025-11678: Stack-based Buffer Overflow in libwebsockets DNS response parsing

> A stack-based buffer overflow in libwebsockets allows attackers to execute code or cause denial of service via crafted DNS responses when async DNS is enabled.

- **Severity:** High 7.5 (`CVSS:4.0/AV:A/AC:L/AT:P/PR:N/UI:P/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** A user has to click or open something
- **Fix available:** Yes
- **Published:** 20 Oct 2025
- **Updated:** 20 Oct 2025
- **Also known as:** BELL-CVE-2025-11678, DEBIAN-CVE-2025-11678, GHSA-2g39-f45w-2fcm, RHSA-2025:22969, UBUNTU-CVE-2025-11678

## What is CVE-2025-11678?

CVE-2025-11678 is a high-severity memory corruption vulnerability in warmcat libwebsocket, published on 20 Oct 2025. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.

### Official description

Stack-based Buffer Overflow in lws_adns_parse_label in warmcat libwebsockets allows, when the LWS_WITH_SYS_ASYNC_DNS flag is enabled during compilation, to overflow the label_stack, when the attacker is able to sniff a DNS request in order to craft a response with a matching id containing a label longer than the maximum.

Weakness: CWE-121 (Stack-based Buffer Overflow)

## Which versions are affected by CVE-2025-11678?


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `libwebsockets` | Red Hat:openstack:17.1::el9 | All versions | 0:4.3.0-2.el9ost |
| `libwebsockets-debuginfo` | Red Hat:openstack:17.1::el9 | All versions | 0:4.3.0-2.el9ost |
| `libwebsockets-debugsource` | Red Hat:openstack:17.1::el9 | All versions | 0:4.3.0-2.el9ost |
| `libwebsockets-devel-debuginfo` | Red Hat:openstack:17.1::el9 | All versions | 0:4.3.0-2.el9ost |

## How do I fix CVE-2025-11678?

Apply the vendor's patch.

## Is CVE-2025-11678 being exploited?

There is no known exploitation of CVE-2025-11678 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2025-11678 and fix it if it is affected.

What it is: CVE-2025-11678 is a high-severity memory corruption vulnerability in warmcat libwebsocket, published on 20 Oct 2025. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.
Exploitation: There is no known exploitation of CVE-2025-11678 in the wild and no public exploit code.

Affected product: warmcat libwebsocket. 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-2025-11678/ (Markdown: https://insights.sbomify.com/CVE-2025-11678/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-11678
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-11678
- OSV: https://osv.dev/vulnerability/CVE-2025-11678

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-11678/
Summaries are generated and may contain mistakes; the official description above is the record.