NATS Server <2.12.8 / <2.11.17: Unauth Peer Crash via Leafnode INFO
CVE-2026-58250 Published on July 8, 2026
NATS Server: Pre-auth server crash via double INFO in leafnode handshake
NATS Server is a high-performance server for NATS.io, the cloud and edge native messaging system. Prior to 2.12.8 and 2.11.17, an unauthenticated peer with network access to a leafnode listener with compression enabled could crash the server during the pre-authentication leafnode handshake by sending repeated leafnode INFO protocol messages before authentication and account setup completed. This issue is fixed in versions 2.12.8 and 2.11.17.
Vulnerability Analysis
CVE-2026-58250 is exploitable with network access, and does not require authorization privileges or user interaction. This vulnerability is considered to have a low attack complexity. The potential impact of an exploit of this vulnerability is considered to have no impact on confidentiality and integrity, and a high impact on availability.
Weakness Type
NULL Pointer Dereference
A NULL pointer dereference occurs when the application dereferences a pointer that it expects to be valid, but is NULL, typically causing a crash or exit. NULL pointer dereference issues can occur through a number of flaws, including race conditions, and simple programming omissions.
Affected Versions
nats-io nats-server:- Version < 2.11.17 is affected.
- Version >= 2.12.0-preview.1, < 2.12.8 is affected.