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.
Affected products
| Vendor | Product | Affected | Fixed |
|---|---|---|---|
| warmcat | libwebsocket | 4.0 – ≤ 4.4.2, 4.0 – ≤ 4.3.6 | — |
Fixed in Linux distributions
Distributions backport fixes, so the version that fixes this vulnerability differs per release — upgrade to at least the version shown. From the distributions' security trackers and advisories.
Debian
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian 14 | libwebsockets | 4.3.5-3 | — |
| Debian 13 | libwebsockets | 4.3.5-1+deb13u1 | — |
| Debian 12 | libwebsockets | No fix yet | — |
| Debian 11 | libwebsockets | 4.0.20-2+deb11u1 | DLA-4373-1 |
Ubuntu
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu 25.10 | libwebsockets | No fix yet | — |
| Ubuntu 22.04 LTS | libwebsockets | 4.0.20-2ubuntu1.1 | USN-8024-1 |
Show 2 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu Pro 24.04 LTS | libwebsockets | 4.3.3-1.1ubuntu0.1~esm1 | USN-8024-1 |
| Ubuntu Pro 20.04 LTS | libwebsockets | 3.2.1-3ubuntu0.1~esm1 | USN-8024-1 |
Red Hat
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Red Hat OpenStack 17 | libwebsockets | 4.3.0-2.el9ost | RHSA-2025:22969 |
Advisories 4
- USN-8024-1 libwebsockets vulnerabilities Ubuntu Security Notices (USN) · Apr 27, 2026
- RHSA-2025:22969 Red Hat Security Advisory: Red Hat OpenStack Platform 17.1 (libwebsockets) security update Red Hat Security Advisories (RHSA) · Mar 18, 2026
- WID-SEC-2025-2784 Red Hat OpenStack Platform (Wallaby): Schwachstelle ermöglicht Codeausführung BSI CERT-Bund (WID) · Feb 11, 2026
- DLA-4373-1 libwebsockets - security update Debian Security (DSA / DLA) · Nov 17, 2025
References
- https://libwebsockets.org/git/libwebsockets/commit?id=2bb9598562b37c942ba5b04bcde3f7fdf66a9d3a patch vendor-advisory
- https://www.nozominetworks.com/labs/vulnerability-advisories-cve-2025-11678 third-party-advisory