CVE-2026-33218 — Improper Input Validation in Nats-server

CWE-20 — Improper Input ValidationCWE-1286 — Improper Validation of Syntactic Correctness of Input8 documents6 sources
Severity
7.5HIGHNVD
EPSS
0.2%
top 55.47%
CISA KEV
Not in KEV
Exploit
No known exploits
Affected products
4
Nats-io Nats-serverLinuxfoundation Nats-serverGithub.com Nats-io Nats-server V2+1 more
Timeline
PublishedMar 25
Latest updateMar 26

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.

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:HExploitability: 3.9 | Impact: 3.6

Affected Packages5 packages

▶debiandebian/nats-server< nats-server 2.12.6-1 (forky)
▶CVEListV5nats-io/nats-server< < 2.11.15+1
▶NVDlinuxfoundation/nats-server2.12.0 — 2.12.6+1
▶Gogithub.com/nats-io_nats-server_v22.12.0-RC.1 — 2.12.6+1
▶Debianlinuxfoundation/nats-server< 2.12.6-1

🔴Vulnerability Details

4
OSV
NATS has pre-auth server panic via leafnode handling in github.com/nats-io/nats-server↗2026-03-26
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OSV
CVE-2026-33218: NATS-Server is a High-Performance server for NATS↗2026-03-25
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GHSA
NATS has pre-auth server panic via leafnode handling↗2026-03-24
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OSV
NATS has pre-auth server panic via leafnode handling↗2026-03-24
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📋Vendor Advisories

2
Red Hat
nats-server: github.com/nats-io/nats-server: NATS-Server: Denial of Service via malformed message pre-authentication on leafnode port↗2026-03-25
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Debian
CVE-2026-33218: nats-server - NATS-Server is a High-Performance server for NATS.io, a cloud and edge native me...↗2026
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🕵️Threat Intelligence

1
Wiz
CVE-2026-33218 Impact, Exploitability, and Mitigation Steps | Wiz↗
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