Advisoriesby Ibisnats-serverGHSA-vprv-35vv-q339
NATS has pre-auth server panic via leafnode handling
No fix yet
Background
NATS.io is a high performance open source pub-sub distributed communication technology, built for the cloud, on-premise, IoT, and edge computing.
The nats-server allows hub/spoke topologies using "leafnode" connections by other nats-servers.
Problem Description
A client which can connect to the leafnode port can crash the nats-server with a certain malformed message pre-authentication.
Affected Versions
Any version before v2.12.6 or v2.11.15
Workarounds
1. Disable leafnode support if not needed.
2. Restrict network connections to your leafnode port, if plausible without compromising the service offered.
References
- This document is canonically: <https://advisories.nats.io/CVE/secnote-2026-10.txt>
- GHSA advisory: <https://github.com/nats-io/nats-server/security/advisories/GHSA-vprv-35vv-q339>
- MITRE CVE entry: <https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2026-33218>
Affected versions
| Package | Affected | Fixed in |
|---|---|---|
| github.com/nats-io/nats-server Go | all versions | No fix yet |
Details and references
- CVSS 3.1
- CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- Severity from
- GitHub (reviewed advisory)
- Weakness
- CWE-20
- Also known as
- BIT-nats-2026-33218, CVE-2026-33218, GO-2026-4837
More nats-server advisories
All nats-server
NATS has mTLS verify_and_map authentication bypass via incorrect Subject DN matchingCVE-2026-33248no fix yetNATS: Leafnode connections allow spoofing of Nats-Request-Info identity headersCVE-2026-33246no fix yetNATS Server: Incomplete Stripping of Nats-Request-Info Header Allows Identity SpoofingCVE-2026-33223no fix yetNATS JetStream has an authorization bypass through its Management APICVE-2026-33222no fix yetNATS is vulnerable to pre-auth DoS through WebSockets client serviceCVE-2026-33219no fix yetNATS allows MQTT clients to bypass ACL checksCVE-2026-33217no fix yet