CVE-2026-33219
NATS is vulnerable to pre-auth DoS through WebSockets client service
- State
- Published
- Severity
- 5.3 Medium
- Published
- Mar 25, 2026
- Updated
- Sep 9, 2026
- Reserved
- Mar 17, 2026
Description
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.
Scores
| CVSS | Score | Vector | Source |
|---|---|---|---|
| 3.1 | 5.3 Medium | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L | 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
- CWE-770 Allocation of Resources Without Limits or Throttling
Affected Products
| Product | Versions |
|---|---|
nats-servernats-io |
|
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
- https://access.redhat.com/security/cve/CVE-2026-33219vdb-entry
- RHBZ#2451445issue-tracking
- https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-33219.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
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