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VulnerabilityPublished

CVE-2026-33215: nats-server · Improper Authentication

Affects nats-serverSource CVE Database V5

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Not known to be exploited · CVSS 6.5 Medium : upgrade to 2.12.6 or 2.11.15 when convenient.

Data as of 30 Oct 2026, 11:52 UTC

CVSS 3.1 base score
6.5Medium
How severe the flaw is on the 0–10 CVSS scale.
EPSS
0.2% chance of exploitation in 30 days – higher than 15% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch
Available – fixed in 2.12.6, 2.11.15
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:L

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 24 Mar 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 30 Oct 2026.

What to do

Upgrade nats-server to 2.12.6 or 2.11.15; nats-io/nats-server to 2.11.15.

Affected software

ProductAffectedFixed in
nats-ionats-serverAffected
  • >=2.12.0-RC.1 <2.12.6
Fixed in
  • 2.12.6
nats-ionats-serverAffected
  • <2.11.15
Fixed in
  • 2.11.15
GitHubnats-io/nats-serverpkg:github/nats-io/nats-serverOther threatsAffected
  • <2.11.15
Fixed in
  • 2.11.15

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

To mitigate CVE-2026-33215, organizations should immediately upgrade nats-server to version 2.11.15 or later, or 2.12.5 or later for 2.12.x branches, as these versions contain the necessary patches. Since no workarounds exist, patching is the only effective defense. Additionally, network segmentation should be enforced to restrict MQTT interface exposure to trusted networks only, minimizing attack surface. Implementing strict access controls and monitoring MQTT client connections for anomalies can help detect potential hijacking attempts. Employing TLS encryption for MQTT traffic can protect data in transit, although it does not prevent client ID spoofing alone. Organizations should also audit their nats-server configurations to disable unnecessary MQTT interfaces if not required. Regularly reviewing logs for unusual client ID usage and integrating intrusion detection systems tailored for MQTT traffic can provide early warning of exploitation attempts. Finally, educating operational teams about this vulnerability and ensuring timely patch management processes are critical to reducing risk.

Description

NATS-Server is a High-Performance server for NATS.io, a cloud and edge native messaging system. The nats-server provides an MQTT client interface. Prior to versions 2.11.15 and 2.12.5, Sessions and Messages can by hijacked via MQTT Client ID malfeasance. Versions 2.11.15 and 2.12.5 patch the issue. No known workarounds are available.

References

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