Skip to content
Fencer Vulns
medium 6.3

CVE-2025-11677 json

Use After Free in libwebsockets WebSocket server

published 2025-10-20 12 mo ago modified 2026-10-08 31 d ago also EUVD-2025-35045

cvss
6.3
version 4.0, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.4%
EPSS 0.4% chance of exploitation in 30 days, percentile 34%
public exploits
0
none known

Summary

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.

Patch / fix

  • libwebsockets Debian 13 4.3.5-1+deb13u1
  • libwebsockets Debian 14 4.3.5-3

debian advisories DEBIAN-CVE-2025-11677

  • libwebsockets Ubuntu 22.04 LTS 4.0.20-2ubuntu1.1
  • libwebsockets Ubuntu Pro 20.04 LTS 3.2.1-3ubuntu0.1~esm1
  • libwebsockets Ubuntu Pro 24.04 LTS 4.3.3-1.1ubuntu0.1~esm1

ubuntu advisories UBUNTU-CVE-2025-11677

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2025-11677 updated cvss 3.7

libwebsockets: Use After Free in libwebsockets WebSocket server

  • Red Hat A-MQ Interconnect 1 libwebsockets Red Hat OpenStack Platform 16.2 libwebsockets Red Hat OpenStack Platform 17.1 libwebsockets Red Hat Service Interconnect 2 libwebsockets
    affected: workaround, no fix available “Fix deferred”

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
none
Automatable
no
Technical impact
partial
Assessed
12 mo ago

Exploit prediction

0.40% chance of exploitation in the next 30 days, higher than 34% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 4.0 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
CNA 4.0 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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

Affected products

  • warmcat libwebsockets

Classification

Weakness

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.