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CVE-2026-27889

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

Published: Mar 25, 2026Updated: Mar 26, 2026 Sources: CVE List NVDCWE-190
NVD MITRE
7.5CVSSHIGH
EPSS Score
0.3%
Top 76.0%
CISA KEV
Not in KEV
Exploits
No Known Exploits
Remediation
Workaround Only

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.

CVSS Vector Breakdown

AV:NAC:LPR:NUI:NS:UC:NI:NA:H
Exploitability
AV:NAttack Vector
Network
AC:LAttack Complexity
Low
PR:NPrivileges Required
None
UI:NUser Interaction
None
Scope
S:UScope
Unchanged
Impact
C:NConfidentiality
None
I:NIntegrity
None
A:HAvailability
High
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Weaknesses

CWE-190

Affected Products

nats-servernats-io
On-prem
Databases / cache-message-queue
nats-serverlinuxfoundation
Mixed
AI / ML / ml-framework
nats-iooss-projectDatabases
linuxfoundationoss-projectUSAI / MLaka yocto, pytorch, everest

Attack Graph

Products CVE Techniques Tactics

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Exploitability

Workaround Available

MITRE ATT&CK

1 technique
Initial Access
View detailed technique mapping

References

https://github.com/nats-io/nats-server/security/advisories/GHSA-pq2q-rcw4-3hr6
github.com
https://advisories.nats.io/CVE/secnote-2026-03.txt
advisories.nats.io

Timeline

Published
Mar 25, 2026
Last Updated
Mar 26, 2026

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