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Advisory record · GHSA-fcjp-h8cc-6879

NATS is vulnerable to MQTT hijacking via Client ID

CVSS 6.5 MediumEPSS 0.0024 · 15th percentile

Published by the GitHub Advisory Database at 24 Mar 2026, 21:39 UTC. agentprime has not analysed this yet, so whether it affects any app is not known.

PackageEcosystemAffectedFixed in
github.com/nats-io/nats-server/v2Go<2.11.15 || >=2.12.0-RC.1, <2.12.62.11.15, 2.12.6
Identifiers
GHSA-fcjp-h8cc-6879 · BIT-nats-2026-33215 · CVE-2026-33215 · GO-2026-4833
Weakness (CWE)
CWE-287 · CWE-488
Tags
Published
24 Mar 2026
Updated
10 Sept 2026

Machine-written summary

Summary written by Claude Haiku from the source advisory. Not reviewed by a person.

NATS server (github.com/nats-io/nats-server/v2) versions before 2.11.15, and 2.12.0-RC.1 through 2.12.5, are affected by a flaw in its MQTT client interface where sessions and messages can be hijacked through the MQTT Client ID. The source gives few details on the exact preconditions. Upgrade to 2.11.15 or 2.12.6; no workaround is listed.

Written 1 Nov 2026.

Not analysed yet

We haven’t published our analysis of this Advisory yet. Once a person has reviewed it, this page will say what’s vulnerable, what has to be true for your app to be affected, and how to check.

Severity and exploitation

ScoreRatingCVSSVectorSource
6.5 Medium 3.1 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:L CNA (GitHub_M)
  • CISA KEV Not listed.
  • EPSS 0.0024, the 15th percentile, on 5 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

Timeline

  1. 31 Oct 2026, 14:13 UTC First seen by agentprime
  2. 31 Oct 2026, 14:13 UTC Confirmed by OSV

Sources

Facts on this page come from the GitHub Advisory Database (CC-BY 4.0), OSV and the other sources listed, as published. We don’t reproduce full advisory descriptions, which can contain exploit code.