Description (CNA)
NATS-Server is a High-Performance server for NATS.io, a cloud and edge native messaging system. Prior to versions 2.11.15 and 2.12.6, a malicious client which can connect to the WebSockets port can cause unbounded memory use in the nats-server before authentication; this requires sending a corresponding amount of data. This is a milder variant of CVE-2026-27571. That earlier issue was a compression bomb, this vulnerability is not. Attacks against this new issue thus require significant client bandwidth. Versions 2.11.15 and 2.12.6 contain a fix. As a workaround, disable websockets if not required for project deployment.
Affected (CNA)
| Vendor / product | Versions |
|---|---|
| nats-io / nats-server | affected < 2.11.15; affected >= 2.12.0-RC.1, < 2.12.6 |
CWE
CWE-770
References
- https://github.com/nats-io/nats-server/security/advisories/GHSA-8r68-gvr4-jh7j
- https://advisories.nats.io/CVE/secnote-2026-02.txt
- https://advisories.nats.io/CVE/secnote-2026-11.txt
- https://github.com/advisories/GHSA-qrvq-68c2-7grw
ADP enrichment
No English description supplied.
No references supplied.
A flaw was found in NATS-Server. A malicious client connecting to the WebSockets port can cause unbounded memory use before authentication by sending a large amount of data. This resource exhaustion vulnerability can lead to a Denial of Service (DoS) for the server, making it unavailable to legitimate users.
- https://access.redhat.com/security/cve/CVE-2026-33219
- https://bugzilla.redhat.com/show_bug.cgi?id=2451445
- https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-33219.json
- https://access.redhat.com/errata/RHSA-2026:22347
- https://access.redhat.com/errata/RHSA-2026:23345
- https://access.redhat.com/errata/RHSA-2026:21769