🛡️ CVE-2026-29785 — nats

🟠 CVSS 8.0 — High ✅ No Known Exploit CWE-476 NVD
8.0
CVSS Score
0 Low4 Medium7 High9 Critical10

Description

NATS Server panic via malicious compression on leafnode port

Background

NATS.io is a high performance open source pub-sub distributed communication technology, built for the cloud, on-premise, IoT, and edge computing.

When configured to accept leafnode connections (for a hub/spoke topology of multiple nats-servers), then the default configuration allows for negotiating compression; a malicious remote NATS server can trigger a server panic via that compression.

Problem Description

If the nats-server has the "leafnode" configuration enabled (not default), then anyone who can connect can crash the nats-server by triggering a panic. This happens pre-authentication and requires that compression be enabled (which it is, by default, when leafnodes are used).

Context: a NATS server can form various clustering topologies, including local clusters, and superclusters of clusters, but leafnodes allow for separate administrative domains to link together with limited data communication; eg, a server in a moving vehicle might use a local leafnode for agents to connect to, and sync up to a central service as and when available. The leafnode configuration here is where the central server allows other NATS servers to connect into it, almost like regular NATS clients. Documentation examples typically use port 7422 for leafnode communications.

Affected Versions

Version 2, prior to v2.11.14 or v2.12.5

Workarounds

Disable compression on the leafnode port:

```

leafnodes {

port: 7422

compression: off

}

```

How this vulnerability can be exploited

This issue can be reached over the network, attack complexity is low, an attacker needs no privileges on the target. No user interaction is required. The scope is unchanged, so the impact stays within the vulnerable component. Rated impact: confidentiality none, integrity none, availability high.

Weakness class

CVE-2026-29785 is classified as CWE-476: NULL Pointer Dereference. A pointer that can be null is used without a check, crashing the process.

Affected software

CVE-2026-29785 is recorded against 4 packages.

  • github.com/nats-io/nats-server
  • github.com/nats-io/nats-server/v2
  • nats
  • nats-server (from 2.12.0 up to 2.12.5)

Timeline and source

Published on 24 March 2026 and last revised on 31 March 2026. No public exploit is currently recorded for this entry. A vendor advisory or fix has been published. Record sourced from NVD.

References

github.com (Web)
nvd.nist.gov (Advisory)
github.com (Web)
advisories.nats.io (Web)
github.com (Package)

CVE-2026-29785 on other distributions

Each distribution ships its own build and its own fixed version. Pick the one you run:

Details

Severity HIGH
CVSS Score 8.0
CVSS Vector CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
CWE CWE-476
Public Exploit ✅ No
Source NVD
Published 2026-03-24
Updated 2026-08-12
Modified 2026-03-31

Affected Packages

Software From version Fixed in
github.com/nats-io/nats-server — —
github.com/nats-io/nats-server/v2 — —
nats — —
nats-server 2.12.0 2.12.5

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