CVE-2026-27889

NameCVE-2026-27889
DescriptionNATS-Server is a High-Performance server for NATS.io, a cloud and edge native messaging system. Starting in version 2.2.0 and prior to versions 2.11.14 and 2.12.5, a missing sanity check on a WebSockets frame could trigger a server panic in the nats-server. This happens before authentication, and so is exposed to anyone who can connect to the websockets port. Versions 2.11.14 and 2.12.5 contains a fix. A workaround is available. The vulnerability only affects deployments which use WebSockets and which expose the network port to untrusted end-points. If one is able to do so, a defense in depth of restricting either of these will mitigate the attack.
SourceCVE (at NVD; CERT, ENISA, LWN, oss-sec, fulldisc, Debian ELTS, Red Hat, Ubuntu, Gentoo, SUSE bugzilla/CVE, GitHub advisories/code/issues, web search, more)

Vulnerable and fixed packages

The table below lists information on source packages.

Source PackageReleaseVersionStatus
nats-server (PTS)bookworm2.9.10-1vulnerable
trixie2.10.27-1vulnerable
forky2.12.4-1vulnerable
sid2.12.6-1vulnerable

The information below is based on the following data on fixed versions.

PackageTypeReleaseFixed VersionUrgencyOriginDebian Bugs
nats-serversource(unstable)(unfixed)

Notes

https://github.com/nats-io/nats-server/security/advisories/GHSA-pq2q-rcw4-3hr6
https://advisories.nats.io/CVE/secnote-2026-03.txt

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