What’s Vulnerable › Vulnerabilities

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

• Severity: high (CVSS 7.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.7% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-07-08 · updated 2026-10-25
• Weakness: CWE-400

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.

Affected products

• nats-io nats-server: before 2.12.12; from 2.14.0 before 2.14.3 — fixed in 2.12.12, 2.14.3

How to fix

Upgrade to a fixed version: nats-io nats-server 2.12.12, 2.14.3. Check the vendor advisory for mitigations.

References

• https://github.com/nats-io/nats-server/commit/bce9ef39469e610aeddb819194ceb7f7edfc0861
• https://github.com/nats-io/nats-server/commit/e016e47bbf70304945f2ae9dc397e4862adefaf5
• https://github.com/nats-io/nats-server/releases/tag/v2.12.12
• https://github.com/nats-io/nats-server/releases/tag/v2.14.3
• https://github.com/nats-io/nats-server/security/advisories/GHSA-r72h-j7qq-v6qg

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