Vulnerability 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.
CVSS Score
MEDIUM
Affected Products
| Vendor | Product | Versions |
|---|---|---|
| Linuxfoundation | Nats-Server | < 2.11.15 |
Related Weaknesses (CWE)
References
- https://advisories.nats.io/CVE/secnote-2026-02.txtMitigationVendor Advisory
- https://advisories.nats.io/CVE/secnote-2026-11.txtMitigationVendor Advisory
- https://github.com/advisories/GHSA-qrvq-68c2-7grwMitigationVendor Advisory
- https://github.com/nats-io/nats-server/security/advisories/GHSA-8r68-gvr4-jh7jMitigationVendor Advisory
FAQ
What is CVE-2026-33219?
CVE-2026-33219 is a vulnerability with a CVSS score of 5.3 (MEDIUM). 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 ca...
How severe is CVE-2026-33219?
CVE-2026-33219 has been rated MEDIUM with a CVSS base score of 5.3/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2026-33219?
Check the references section above for vendor advisories and patch information. Affected products include: Linuxfoundation Nats-Server.