Resource exhaustion in Linuxfoundation Nats-Server

CVE-2026-33219

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.

Published · last modified .

CVSS v3 metric

CVSS v3 base score 5.3 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L.

EPSS exploit prediction

EPSS: 0.010 (61.5th percentile), scored .

Low probability of exploitation in the next 30 days, but still tracked. 62nd percentile — 61.5% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS trend (30 days)EPSS over the last 30 days for CVE-2026-33219: held from 0.005 to 0.010.

EPSS over last 30 days · oldest: 0.005 · newest: 0.010 · change: +0.005

Affected products

Weakness classification (CWE)

References

Frequently asked questions

What is CVE-2026-33219?
CVE-2026-33219 is a medium-severity vulnerability in Linuxfoundation Nats-Server, classified under Allocation of Resources Without Limits or Throttling. CVSS score: 5.3/10. Published 2026-03-25.
How severe is CVE-2026-33219?
Medium severity. CVSS v3 base score is 5.3 out of 10.