GO-2026-4829Published

NATS Server panic via malicious compression on leafnode port

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cve-program · CVE-2026-29785

Published

NATS-Server is a High-Performance server for NATS.io, a cloud and edge native messaging system. Prior to versions 2.11.14 and 2.12.5, 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). Versions 2.11.14 and 2.12.5 contain a fix. As a workaround, disable compression on the leafnode port.

Source published: 25 Mar 2026 19:38:44 UTC
Source modified: 9 Sep 2026 12:04:53 UTC
Saved here: 23 Oct 2026 15:48:27 UTC
Source terms: CVE Program Terms of Use

Original source record · Cite this exact observation · Complete original publisher JSON

Source: cve-program · CVE Program Terms of Use. The publisher's wording is preserved. ChangeIntel groups the information and labels changes. The JSON record includes additional source fields.

CVSS 3.1 · 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

euvd · EUVD-2026-15963

Published

Additional publisher context

EUVD source date text has no stated timezone and is retained without inventing a UTC instant. Related bulletin membership is not an alias, common cause or applicability claim. A missing vector with a zero score is treated as unrated. Complete vendor/product and underlying source evidence remains in the original JSON.

Original publisher date fields

datePublished: Mar 25, 2026, 7:38:44 PM

dateUpdated: Sep 9, 2026, 12:04:53 PM

5 related source bulletins · separate from aliases

RHSA-2026:22347: Red Hat Security Advisory: Multicluster Global Hub 1.4.5 security update

CVE-2026-4427 · CVE-2026-21728 · CVE-2026-25679 · CVE-2026-27137 · CVE-2026-27889 · CVE-2026-29785 · CVE-2026-32280 · CVE-2026-32281 · CVE-2026-32282 · CVE-2026-32283 · CVE-2026-32285 · CVE-2026-32286 · CVE-2026-33186 · CVE-2026-33215 · CVE-2026-33216 · CVE-2026-33217 · CVE-2026-33218 · CVE-2026-33219 · CVE-2026-33247 · CVE-2026-33413 · CVE-2026-33487 · CVE-2026-33810 · CVE-2026-33813 · CVE-2026-33997 · CVE-2026-34040 · CVE-2026-34986 · CVE-2026-40890 · CVE-2026-41602 · CVE-2026-41603 · CVE-2026-41604 · CVE-2026-41605 · CVE-2026-41606 · CVE-2026-41607 · CVE-2026-41636 · CVE-2026-43869

RHSA-2026:21769: Red Hat Security Advisory: Multicluster Global Hub 1.5.4 security update

msrc_CVE-2026-29785: NATS Server panic via malicious compression on leafnode port

CVE-2026-29785

WID-SEC-W-2026-0641: NATS Server: Mehrere Schwachstellen ermöglichen Denial of Service

CVE-2026-27889 · CVE-2026-29785

RHSA-2026:23345: Red Hat Security Advisory: Multicluster Global Hub 1.6.2 security update

Source published: Mar 25, 2026, 7:38:44 PM (timezone not stated)
Source modified: Sep 9, 2026, 12:04:53 PM (timezone not stated)
Saved here: 15 Nov 2026 09:29:42 UTC
Source terms: ENISA EUVD · source terms and attribution apply

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Source: euvd · ENISA EUVD · source terms and attribution apply. The publisher's wording is preserved. ChangeIntel groups the information and labels changes. The JSON record includes additional source fields.

EUVD CVSS 3.1 · 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

nvd · CVE-2026-29785

Published

Additional publisher context

NVD analysis and CPE criteria are source context, not proof that a package or your environment is affected. Complete affected data, logical configurations and SSVC are retained in the original JSON.

Source analysis status: Modified

Weakness classifications: CWE-476 · CWE-409

Original publisher date fields

published: 2026-03-25T20:16:30.373

lastModified: 2026-09-09T13:19:11.863

1 source CPE criteria · context only

cpe:2.3:a:linuxfoundation:nats-server:*:*:*:*:*:*:*:*

The original JSON retains the logical configuration operators, exclusions and version bounds.

Source published: 25 Mar 2026 20:16:30 UTC
Source modified: 9 Sep 2026 13:19:11 UTC
Saved here: 25 Oct 2026 07:19:08 UTC
Source terms: NIST NVD usage terms; underlying source attribution retained

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CVSS 3.1 · [email protected] · Secondary · 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CVSS 3.1 · 0b0ca135-0b70-47e7-9f44-1890c2a1c46c · Secondary · 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

osv · GHSA-52jh-2xxh-pwh6

Published

### 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 } ```

Source published: 24 Mar 2026 21:29:06 UTC
Source modified: 10 Sep 2026 03:50:59 UTC
Saved here: 24 Oct 2026 13:19:41 UTC
Source terms: GitHub Advisory Database · CC-BY-4.0

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CVSS_V3 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Publisher rating · HIGH

osv · GO-2026-4829

Published

NATS Server panic via malicious compression on leafnode port in github.com/nats-io/nats-server

Source published: 26 Mar 2026 20:33:05 UTC
Source modified: 31 Mar 2026 05:29:17 UTC
Saved here: 24 Oct 2026 13:19:41 UTC
Source terms: OSV · upstream source license applies

Original source record · Cite this exact observation · Complete original publisher JSON

Source: osv · OSV · upstream source license applies. The publisher's wording is preserved. ChangeIntel groups the information and labels changes. The JSON record includes additional source fields.