High 7.5Published Mar 25, 2026

CVE-2026-27889NATS: Pre-auth remote server crash via WebSocket frame length overflow in wsRead

Updated under an hour ago (Oct 26, 2026, 10:30 PM ET)

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It affects nats-io nats-server and 3 other products. Add what you run to find out whether that includes you.

No exploitation reported and no EPSS estimate yet.

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Every CVE for nats-io nats-server

Exploited in the last 30 days

NATS-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.

CVSS: 7.5 HIGH (v3.1, CNA)CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Weakness (CWE): CWE-190, CWE-1286
Known exploited: Not in CISA's KEV catalog
EPSS (exploitation in the next 30 days): Not loaded for this CVE
Assigned by: GitHub_M
NVD analysis: Modified
Record last updated: Sep 9, 2026
First seen by InfoSec Signals: Oct 9, 2026

Affected products

Affected products

nats-io nats-server nats_io:nats_server (from the name)	from 2.2.0, < 2.11.14; from 2.12.0, < 2.12.5	CNA record
Red Hat Multicluster Global Hub 1.4.5 redhat:multicluster_globalhub	from 1779579439 not affected	CISA ADP
Red Hat Red Hat OpenShift Container Platform 4 redhat:openshift	4	CISA ADP
linuxfoundation nats-server linuxfoundation:nats-server	from 2.2.0 before 2.11.14; from 2.12.0 before 2.12.5	NVD

References

References

https://github.com/nats-io/nats-server/security/advisories/GHSA-pq2q-rcw4-3hr6	x-refsource-confirm, mitigation, vendor-advisory
https://advisories.nats.io/CVE/secnote-2026-03.txt	x-refsource-misc, mitigation, vendor-advisory
https://access.redhat.com/errata/RHSA-2026:21769
https://access.redhat.com/errata/RHSA-2026:22347
https://access.redhat.com/errata/RHSA-2026:23345
https://access.redhat.com/security/cve/CVE-2026-27889
https://bugzilla.redhat.com/show_bug.cgi?id=2451447
https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-27889.json

The CVE record on cve.org NVD's entry

The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.