CVE-2026-58250 NATS Server: Pre-auth server crash via double INFO in leafnode handshake

What is CVE-2026-58250?

CVE-2026-58250 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 2.12.8 and 2.11.17, an unauthenticated peer with network access to a leafnode listener with compression enabled could crash the server during the pre-authentication leafnode handshake by sending repeated leafnode INFO protocol messages before authentication and account setup completed. This issue is fixed in versions 2.12.8 and 2.11.17.

Weakness: CWE-476

Which versions are affected by CVE-2026-58250?

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

Products include Linuxfoundation Nats-Server.

How do I fix CVE-2026-58250?

Upgrade nats to a fixed version for your release line: 2.11.17 or 2.12.8.

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-2026-58250 being exploited?

There is no known exploitation of CVE-2026-58250 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 AZL-92250, BIT-nats-2026-58250, DEBIAN-CVE-2026-58250, GHSA-3g5q-cfh2-cq67, JLSEC-2026-1150, MINI-8f7v-gpr2-jr6x and 2 more.