GHSA-vprv-35vv-q339
NATS has pre-auth server panic via leafnode handling
Quick fix
GHSA-vprv-35vv-q339 — github.com/nats-io/nats-server/v2: upgrade to the fixed version with the command below.
go get github.com/nats-io/nats-server/v2@v2.11.15Details
### 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>
Are you affected?
Enter the version of the package you're using.
Affected packages
0Fixed in: 2.11.15go get github.com/nats-io/nats-server/v2@v2.11.152.12.0-RC.1Fixed in: 2.12.6go get github.com/nats-io/nats-server/v2@v2.12.60No fixed version published yet for github.com/nats-io/nats-server (go modules). Pin to a known-safe version or switch to an alternative.