CVE-2026-33219

Summary

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.

Affected Software

Weaknesses

• CWE-770: CWE-770: Allocation of Resources Without Limits or Throttling

ADP Enrichment

CISA ADP Vulnrichment

• SSVC:
• Exploitation: none
  • Automatable: no
  • Technical Impact: partial

github.com/nats-io/nats-server: NATS-Server: Denial of Service via unbounded memory use in WebSockets

Additional References

• 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
• https://access.redhat.com/errata/RHSA-2026:22347
• https://access.redhat.com/errata/RHSA-2026:21769
• https://access.redhat.com/errata/RHSA-2026:23345

References

• https://github.com/nats-io/nats-server/security/advisories/GHSA-8r68-gvr4-jh7j
• https://advisories.nats.io/CVE/secnote-2026-02.txt
• https://advisories.nats.io/CVE/secnote-2026-11.txt
• https://github.com/advisories/GHSA-qrvq-68c2-7grw

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