CVE-2026-58214 NATS Server: MQTT subscribe ACL bypass via $MQTT.deliver.pubrel prefix (incomplete fix for CVE-2026-33217)

What is CVE-2026-58214?

CVE-2026-58214 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, 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.

Weakness: CWE-863

Which versions are affected by CVE-2026-58214?

1 open source package ship an affected version, including nats. It affects 1 product.

Products include Linuxfoundation Nats-Server.

How do I fix CVE-2026-58214?

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-2026-58214 being exploited?

There is no known exploitation of CVE-2026-58214 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 Critical 9.8
• CVE-2026-58253 NATS Server: Route API Auth Bypass High 8.8
• CVE-2022-24450 Incorrect Authorization in NATS nats-server High 8.8
• CVE-2026-33216 NATS has MQTT plaintext password disclosure High 8.6
• CVE-2026-58207 NATS Server: Remote crash via integer overflow in Connz pagination High 7.7

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as BIT-nats-2026-58214, DEBIAN-CVE-2026-58214, GHSA-4g68-3pwx-5vfj, JLSEC-2026-1149, MINI-cf24-x4mx-cfq2, MINI-w67j-5c9c-qxpr and 1 more.