Auth bypass in Linuxfoundation Nats-Server
CVE-2026-58209
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, MQTT retained message delivery and QoS1+ durable replay could deliver messages whose original topics matched a subscriber configured subscribe deny rule because these delivery paths did not consistently recheck the concrete original topic before sending the MQTT PUBLISH to the subscriber. 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 (25.7th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 26th percentile — 25.7% 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/181b1f51f40b9954c57e9d478e051fb257679356 (Patch)
- github.com/nats-io/nats-server/commit/1c429b6fdc5afd4188cc5faf1127f6334896cd87 (Patch)
- github.com/nats-io/nats-server/releases/tag/v2.12.12 (Product, Release Notes)
- github.com/nats-io/nats-server/releases/tag/v2.14.3 (Product, Release Notes)
- github.com/nats-io/nats-server/security/advisories/GHSA-7qmq-8cc4-hxwg (Vendor Advisory)
Frequently asked questions
- What is CVE-2026-58209?
- CVE-2026-58209 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-2026-58209?
- Medium severity. CVSS v3 base score is 4.3 out of 10.