CVE-2026-33218

NATS has pre-auth server panic via leafnode handling

State: Published
Severity: 7.5 High
Published: Mar 25, 2026
Updated: Sep 9, 2026
Reserved: Mar 17, 2026

Description

NATS-Server is a High-Performance server for NATS.io, a cloud and edge native messaging system. Prior to versions 2.11.15 and 2.12.6, a client which can connect to the leafnode port can crash the nats-server with a certain malformed message pre-authentication. Versions 2.11.15 and 2.12.6 contain a fix. As a workaround, disable leafnode support if not needed or restrict network connections to the leafnode port, if plausible without compromising the service offered.

Scores

CVSS	Score	Vector	Source
3.1	7.5 High	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H	GitHub_M
3.1	7.5 High	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H	redhat-SADP

Weaknesses

CWE-20 Improper Input Validation
CWE-1286 Improper Validation of Syntactic Correctness of Input

Affected Products

Product	Versions
nats-servernats-io	< < 2.11.15Affected >= 2.12.0-RC.1, < 2.12.6Affected

References

https://github.com/nats-io/nats-server/security/advisories/GHSA-vprv-35vv-q339
https://advisories.nats.io/CVE/secnote-2026-10.txt
https://access.redhat.com/security/cve/CVE-2026-33218vdb-entry
RHBZ#2451450issue-tracking
https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-33218.json
https://access.redhat.com/errata/RHSA-2026:22347vendor-advisory
https://access.redhat.com/errata/RHSA-2026:23345vendor-advisory
https://access.redhat.com/errata/RHSA-2026:21769vendor-advisory

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