CVE-2026-29785: nats-io nats-server NULL pointer dereference in leafnode protocol

CVE-2026-29785 · Severity: high · CVSS 7.5 · Published 2026-03-25

NATS-Server, a high-performance messaging system used for cloud and edge computing, is vulnerable to a denial-of-service attack. If the 'leafnode' feature is enabled, an unauthenticated remote attacker can crash the server by sending specific commands before the connection is fully established. This results in a complete service outage, potentially disrupting data communication between distributed systems or IoT devices.

Technologies: github.com/nats-io/nats-server (Go), github.com/nats-io/nats-server/v2 (Go), Red Hat Multicluster Global Hub. Vendors: Go, Red Hat.

Quick answers

Is CVE-2026-29785 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2026-29785 being exploited in the wild.
How severe is CVE-2026-29785?
High severity, with a CVSS score of 7.5, published 25 March 2026.
Which products and versions are affected?
github.com/nats-io/nats-server (Go) SEMVER:introduced=0; github.com/nats-io/nats-server/v2 (Go) SEMVER:introduced=0,fixed=2.11.14, SEMVER:introduced=0,fixed=2.11.14,introduced=2.12.0-RC.1,fixed=2.12.5; Red Hat Multicluster Global Hub 1.4.5, 1.5.4, 1.6.2.
Is there a fix for CVE-2026-29785?
Yes. github.com/nats-io/nats-server/v2 (Go): upgrade to 2.11.14, 2.12.5 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-29785 attacked?
It is attacked over the network, in a software library.
Am I affected by CVE-2026-29785?
Check whether you run github.com/nats-io/nats-server (Go), github.com/nats-io/nats-server/v2 (Go) or Red Hat Multicluster Global Hub at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

How to fix

  • github.com/nats-io/nats-server/v2 (Go): upgrade to 2.11.14, 2.12.5 or later
    go get github.com/nats-io/nats-server/v2@v2.12.5

Technical details

A NULL pointer dereference (CWE-476) exists in NATS-Server's leafnode protocol handling. When compression is enabled on a leafnode port (typically 7422), the server may process 'LS+' (Leafnode Subscribe) commands before the 'CONNECT' command has been fully processed, leading to a nil pointer access for the client account object. This vulnerability is reachable over the network without authentication. The issue is fixed in versions 2.11.14 and 2.12.5. A known workaround is to disable compression within the leafnodes configuration block.

Affected products

  • nats-io nats-server < 2.11.14, >= 2.12.0-RC.1 < 2.12.5
  • Red Hat Multicluster Global Hub 1.4.5, 1.5.4, 1.6.2

Identifiers

  • CVE-2026-29785
  • GHSA-52jh-2xxh-pwh6
  • GO-2026-4829

Timeline

  • 2026-03-02: other: Fix authored by maintainers
  • 2026-03-09: advisory: Internal advisory date
  • 2026-03-25: disclosed: Public disclosure of CVE-2026-29785
  • 2026-03-25: patched: Fixed versions released

References

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