CVE-2026-58209 NATS Server: MQTT retained and QoS replay bypass subscribe deny filters
Attackers can bypass subscribe deny filters to receive unauthorized MQTT retained or replayed messages in NATS Server.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-58209?
CVE-2026-58209 is a medium-severity missing authorization vulnerability in nats-io nats-server, published on 8 Jul 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Official description
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.
Weakness: CWE-863
Which versions are affected by CVE-2026-58209?
1 open source package ship an affected version, including nats. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
nats Bitnami | All versions | 2.12.12, 2.14.3 |
Products include Linuxfoundation Nats-Server.
How do I fix CVE-2026-58209?
Upgrade nats to a fixed version for your release line: 2.12.12 or 2.14.3.
Upgrade, and check permissions on every request on the server, not only in the interface. More about Missing authorization.
Is CVE-2026-58209 being exploited?
There is no known exploitation of CVE-2026-58209 in the wild and no public exploit code.
Other vulnerabilities in nats-io nats-server
- CVE-2022-28357 NATS nats-server allows directory traversal via unintended path to a management action
- CVE-2026-58253 NATS Server: Route API Auth Bypass
- CVE-2022-24450 Incorrect Authorization in NATS nats-server
- CVE-2026-33216 NATS has MQTT plaintext password disclosure
- CVE-2026-58207 NATS Server: Remote crash via integer overflow in Connz pagination
Sources
Also known as AZL-92256, BIT-nats-2026-58209, DEBIAN-CVE-2026-58209, GHSA-7qmq-8cc4-hxwg, JLSEC-2026-1146, MINI-c2c3-6rqc-pwvw and 2 more.