CVE-2026-27889
NATS: Pre-auth remote server crash via WebSocket frame length overflow in wsRead
- State
- Published
- Severity
- 7.5 High
- Published
- Mar 25, 2026
- Updated
- Sep 9, 2026
- Reserved
- Feb 24, 2026
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.
Scores
| CVSS | Score | Vector | Source |
|---|---|---|---|
| 3.1 | 7.5 High | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H | GitHub_M |
| 3.1 | 7.5 High | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H | redhat-SADP |
Weaknesses
Affected Products
| Product | Versions |
|---|---|
nats-servernats-io |
|
References
- https://github.com/nats-io/nats-server/security/advisories/GHSA-pq2q-rcw4-3hr6
- https://advisories.nats.io/CVE/secnote-2026-03.txt
- https://access.redhat.com/security/cve/CVE-2026-27889vdb-entry
- RHBZ#2451447issue-tracking
- https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-27889.json
- https://access.redhat.com/errata/RHSA-2026:22347vendor-advisory
- https://access.redhat.com/errata/RHSA-2026:23345vendor-advisory
- https://access.redhat.com/errata/RHSA-2026:21769vendor-advisory
Every record here comes from the CVE Program’s CVE List. © 1999–2026 The MITRE Corporation. CVE is a registered trademark of The MITRE Corporation. The records are reproduced under the CVE Program terms of use.