NATS: Pre-auth remote server crash via WebSocket frame length overflow in wsRead

Summary

CVE	CVE-2026-27889
State	PUBLISHED
Assigner	GitHub_M
Source Priority	CVE Program / NVD first with legacy fallback
Published	2026-03-25 20:16:27 UTC
Updated	2026-06-30 03:17:59 UTC
Description	NATS-Server is a High-Performance server for NATS.io, a cloud and edge native messaging system. Starting in version 2.2.0 and prior to versions 2.11.14 and 2.12.5, a missing sanity check on a WebSockets frame could trigger a server panic in the nats-server. This happens before authentication, and so is exposed to anyone who can connect to the websockets port. Versions 2.11.14 and 2.12.5 contains a fix. A workaround is available. The vulnerability only affects deployments which use WebSockets and which expose the network port to untrusted end-points. If one is able to do so, a defense in depth of restricting either of these will mitigate the attack.

Risk And Classification

Primary CVSS: v3.1 7.5 HIGH from ADP

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

Problem Types: CWE-190 | CWE-1286 | CWE-190 CWE-190: Integer Overflow or Wraparound | CWE-1286 Improper Validation of Syntactic Correctness of Input

Version	Source	Type	Score	Severity	Vector
3.1	ADP	CVSS	7.5	HIGH	`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`
3.1	[email protected]	Secondary	7.5	HIGH	`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`
3.1	0b0ca135-0b70-47e7-9f44-1890c2a1c46c	Secondary	7.5	HIGH	`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`
3.1	CNA	DECLARED	7.5	HIGH	`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`

CVSS v3.1 Breakdown

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

None

Scope

Unchanged

Confidentiality

None

Integrity

None

Availability

High

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

NVD Known Affected Configurations (CPE 2.3)

Type	Vendor	Product	Version	Update	Edition	Language
Application	Linuxfoundation	Nats-server	All	All	All	All

Vendor Declared Affected Products

Source	Vendor	Product	Version	Platforms
CNA	Nats-io	Nats-server	affected >= 2.2.0, < 2.11.14	Not specified
CNA	Nats-io	Nats-server	affected >= 2.12.0, < 2.12.5	Not specified
ADP	Red Hat	Multicluster Global Hub 1.4.5	Not specified	Not specified
ADP	Red Hat	Multicluster Global Hub 1.5.4	Not specified	Not specified
ADP	Red Hat	Multicluster Global Hub 1.6.2	Not specified	Not specified
ADP	Red Hat	Red Hat OpenShift Container Platform 4	Not specified	Not specified

References

Reference	Source	Link	Tags
security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-27889.json	0b0ca135-0b70-47e7-9f44-1890c2a1c46c	security.access.redhat.com
access.redhat.com/security/cve/CVE-2026-27889	0b0ca135-0b70-47e7-9f44-1890c2a1c46c	access.redhat.com
access.redhat.com/errata/RHSA-2026:21769	0b0ca135-0b70-47e7-9f44-1890c2a1c46c	access.redhat.com
github.com/nats-io/nats-server/security/advisories/GHSA-pq2q-rcw4-3hr6	[email protected]	github.com	Mitigation, Vendor Advisory
access.redhat.com/errata/RHSA-2026:23345	0b0ca135-0b70-47e7-9f44-1890c2a1c46c	access.redhat.com
advisories.nats.io/CVE/secnote-2026-03.txt	[email protected]	advisories.nats.io	Mitigation, Vendor Advisory
bugzilla.redhat.com/show_bug.cgi	0b0ca135-0b70-47e7-9f44-1890c2a1c46c	bugzilla.redhat.com
access.redhat.com/errata/RHSA-2026:22347	0b0ca135-0b70-47e7-9f44-1890c2a1c46c	access.redhat.com
CVE Program record	CVE.ORG	www.cve.org	canonical
NVD vulnerability detail	NVD	nvd.nist.gov	canonical, analysis

No vendor comments have been submitted for this CVE.

Additional Advisory Data

Source	Time	Event
ADP	2026-03-25T20:01:58.261Z	Reported to Red Hat.
ADP	2026-03-25T19:36:36.370Z	Made public.

Solutions

ADP: RHSA-2026:22347: Multicluster Global Hub 1.4.5

ADP: RHSA-2026:21769: Multicluster Global Hub 1.5.4

ADP: RHSA-2026:23345: Multicluster Global Hub 1.6.2

Workarounds

ADP: Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base or stability.

There are currently no legacy QID mappings associated with this CVE.