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.
Does this matter?
High impact if exploited, but EPSS currently rates exploitation as unlikely (0.58%). 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
- 0.58% probability · 46th percentile
- CISA KEV
- Not listed
- Weakness
- CWE-190, CWE-1286
- Affected
- linuxfoundation/nats-server
- Source
- security-advisories@github.com
References
- https://advisories.nats.io/CVE/secnote-2026-03.txtMitigation, Vendor Advisory
- https://github.com/nats-io/nats-server/security/advisories/GHSA-pq2q-rcw4-3hr6Mitigation, Vendor Advisory
- https://access.redhat.com/errata/RHSA-2026:21769
- https://access.redhat.com/errata/RHSA-2026:22347
- https://access.redhat.com/errata/RHSA-2026:23345
- https://access.redhat.com/security/cve/CVE-2026-27889
- https://bugzilla.redhat.com/show_bug.cgi?id=2451447
- https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-27889.json
Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.