Auth bypass in Linuxfoundation Nats-Server
CVE-2026-58214
NATS Server is a high-performance server for NATS.io, the cloud and edge native messaging system. Prior to 2.14.3 and 2.12.12, an authenticated MQTT client could subscribe to the internal $MQTT.deliver.pubrel subject family, bypassing configured subscribe permissions and exposing MQTT QoS2 protocol metadata for sessions in the account. This issue is fixed in versions 2.14.3 and 2.12.12.
Vulnerability class: Broken Access Control
Published · last modified .
CVSS v3 metric
CVSS v3 base score 4.3 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N.
EPSS exploit prediction
EPSS: 0.003 (26.4th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 26th percentile — 26.4% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.003 · newest: 0.003 · change: 0.000
Affected products
- Linuxfoundation Nats-Server
- Nats-Io Nats-Server — versions < 2.12.12, >= 2.14.0-RC.1, < 2.14.3
Weakness classification (CWE)
References
- github.com/nats-io/nats-server/commit/297b166be60fe13144084eed4b25201ead03204a (Patch)
- github.com/nats-io/nats-server/commit/34b09657bb596d5f850eaa5cfc97ea6b2f989a97 (Patch)
- github.com/nats-io/nats-server/releases/tag/v2.12.12 (Release Notes)
- github.com/nats-io/nats-server/releases/tag/v2.14.3 (Release Notes)
- github.com/nats-io/nats-server/security/advisories/GHSA-4g68-3pwx-5vfj (Vendor Advisory)
Frequently asked questions
- What is CVE-2026-58214?
- CVE-2026-58214 is a medium-severity vulnerability in Linuxfoundation Nats-Server, classified under Incorrect Authorization. CVSS score: 4.3/10. Published 2026-07-08.
- How severe is CVE-2026-58214?
- Medium severity. CVSS v3 base score is 4.3 out of 10.