CVE-2026-33219NATS-Server is a High-Performance server for NATS.io, a cloud and edge native messaging system.
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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.
- CVSS
- 5.3 MEDIUM (v3.1, NVD)CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
- Weakness (CWE)
- CWE-770
- Known exploited
- Not in CISA's KEV catalog
- EPSS (exploitation in the next 30 days)
- Not loaded for this CVE
- Assigned by
- Not given
- NVD analysis
- Modified
- Record last updated
- Sep 9, 2026
- First seen by InfoSec Signals
- Oct 9, 2026
Affected products
linuxfoundation nats-server linuxfoundation:nats-server | before 2.11.15; from 2.12.0 before 2.12.6 | NVD |
References
- https://advisories.nats.io/CVE/secnote-2026-02.txtmitigation, vendor-advisory
- https://advisories.nats.io/CVE/secnote-2026-11.txtmitigation, vendor-advisory
- https://github.com/advisories/GHSA-qrvq-68c2-7grwmitigation, vendor-advisory
- https://github.com/nats-io/nats-server/security/advisories/GHSA-8r68-gvr4-jh7jmitigation, 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-2026-33219
- https://bugzilla.redhat.com/show_bug.cgi?id=2451445
- https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-33219.json
The CVE record on cve.org NVD's entry
The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.