CVE-2026-33218

NATS has pre-auth server panic via leafnode handling

HIGH
7.5
CVSS Score
Published: March 25, 2026 at 07:53 PM UTC
Updated: September 9, 2026 at 01:19 PM UTC
2 products affected across 2 vendorsNats ServerNats Server

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Severity
HIGH7.5
Exploit prediction
EPSS 0.6%
SSVC
No known exploit

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.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

v < 2.11.152.12.0 ≤ v < 2.12.6
Affected range stops below 2.11.15, so it looks safe — our inference, not a vendor statement
Affected range stops below 2.12.6, so it looks safe — our inference, not a vendor statement
v < 2.11.15v < 2.12.6
Affected range stops below 2.11.15, so it looks safe — our inference, not a vendor statement
Affected range stops below 2.12.6, so it looks safe — our inference, not a vendor statement

Remediation

No guide yet

No remediation guidance has been written for this CVE yet. What the record does show:

References (8)

x_refsource_CONFIRMMitigationVendor Advisory
Source: cverecord
https://github.com/nats-io/nats-server/security/advisories/GHSA-vprv-35vv-q339
x_refsource_MISCMitigationVendor Advisory
Source: cverecord
https://advisories.nats.io/CVE/secnote-2026-10.txt
Source: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
https://access.redhat.com/errata/RHSA-2026:21769
Source: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
https://access.redhat.com/errata/RHSA-2026:22347
Source: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
https://access.redhat.com/errata/RHSA-2026:23345
Source: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
https://access.redhat.com/security/cve/CVE-2026-33218
Source: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
https://bugzilla.redhat.com/show_bug.cgi?id=2451450

SSVC — Action Prioritization

SSVCNo known exploitAutomatablePartial impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

7.5HIGHGitHub_M
Attack Vector
NETWORK
Complexity
LOW
Privileges
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality
NONE
Integrity
NONE
Availability
HIGH
Vector?

Quick Info

StatusMODIFIED
CWE
CWE-20CWE-1286

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