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Vulnerability record · CVE-2026-27889 · published 25 March 2026

CVE-2026-27889: Linuxfoundation nats-server integer overflow vulnerability

Linuxfoundation · Nats Server

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.

7.5 CVSS 3.1 High EPSS 0.84% · top 43.7% CWE-190 · Integer overflowCWE-1286 · CWE-1286
7.5CVSS 3.1 base score
0.84%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
8References
9 Sep 2026Last modified by NVD

Description

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:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Affected products

1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

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

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Related vulnerabilities

Same products first, then exploited flaws of the same weakness class.

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Source: NIST National Vulnerability Database (record CVE-2026-27889), CISA KEV, FIRST EPSS (scores of 2026-09-27). This page is refreshed as NVD updates the record.