VulnerabilityModified

CVE-2026-27889

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.

HIGH 7.5EPSS 0.59%

Does this matter?

High impact if exploited, but EPSS currently rates exploitation as unlikely (0.59%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit.

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 3.1: 7.5 HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
EPSS: 0.59% probability · 48th percentile
Public exploits: None in Exploit-DB
CISA KEV: Not listed
Weakness: CWE-190, CWE-1286
Affected: linuxfoundation/nats-server
Source: security-advisories@github.com

EPSS trend

EPSS 0.6% since 26 October 2026; no change recorded yet. Points are recorded when the score first appears and whenever it moves by a percentage point or more.

References

Source: NVD record, EPSS from FIRST.org, KEV from CISA, exploits from Exploit-DB. Refreshed daily. Download this record as JSON.