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Security Advisories

CVE-2026-33219

NVD

https://nvd.nist.gov/vuln/detail/CVE-2026-33219

Severity

5.3

Medium

CVSS V3

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Summary

NATS is vulnerable to pre-auth DoS through WebSockets client service

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.

References

Affected packages

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