CVE-2026-58210 NATS Server: MQTT partial CONNECT packets can exhaust pre-auth memory

What is CVE-2026-58210?

CVE-2026-58210 is a high-severity denial of service vulnerability in nats-io nats-server, published on 8 Jul 2026. An attacker can exploit it over the internet without logging in, 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 unauthenticated MQTT client could cause the server to retain large incomplete MQTT CONNECT packets before authentication completed, consuming server memory while the parser waited for the advertised MQTT packet length. This issue is fixed in versions 2.14.3 and 2.12.12.

Weakness: CWE-400

Which versions are affected by CVE-2026-58210?

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

Products include Linuxfoundation Nats-Server.

How do I fix CVE-2026-58210?

Upgrade nats to a fixed version for your release line: 2.12.12 or 2.14.3.

Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.

Is CVE-2026-58210 being exploited?

There is no known exploitation of CVE-2026-58210 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-2026-58210, DEBIAN-CVE-2026-58210, GHSA-r72h-j7qq-v6qg, JLSEC-2026-1147, MINI-79cc-5hpg-8vrr, MINI-qv4w-48hf-74vj and 1 more.