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CVE-2026-33219

MEDIUM

5.3

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.

CVE Details

CVSS v3.1 Score5.3

SeverityMEDIUM

CVSS VectorCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

Attack VectorNETWORK

ComplexityLOW

Privileges RequiredNONE

User InteractionNONE

Published3/25/2026

Last Modified3/26/2026

Sourcenvd

Honeypot Sightings0

Affected Products

linuxfoundation:nats-server

Weaknesses (CWE)

CWE-770

References

https://advisories.nats.io/CVE/secnote-2026-02.txt(security-advisories@github.com)

https://advisories.nats.io/CVE/secnote-2026-11.txt(security-advisories@github.com)

https://github.com/advisories/GHSA-qrvq-68c2-7grw(security-advisories@github.com)

https://github.com/nats-io/nats-server/security/advisories/GHSA-8r68-gvr4-jh7j(security-advisories@github.com)

IOC Correlations

No correlations recorded

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