Unauthenticated MQTT Client Vulnerability in NATS Server
CVE-2026-58210

7.5HIGH

Key Information:

Vendor

Nats-io

Status
Nats-server
Vendor
CVE Published:
8 July 2026

What is CVE-2026-58210?

An unauthenticated MQTT client could exploit a flaw in versions of NATS Server before 2.14.3 and 2.12.12 by sending large incomplete MQTT CONNECT packets. This could lead to excessive memory consumption on the server while waiting for the complete MQTT packet length, which could impair server performance. The vulnerability has been addressed in the latest versions.

Affected Version(s)

nats-server < 2.12.12 < 2.12.12

nats-server >= 2.14.0-RC.1, < 2.14.3 < 2.14.0-RC.1, 2.14.3

References

https://github.com/nats-io/nats-server/security/advisorie...
x_refsource_CONFIRM
https://github.com/nats-io/nats-server/commit/bce9ef39469...
x_refsource_MISC
https://github.com/nats-io/nats-server/commit/e016e47bbf7...
x_refsource_MISC

CVSS V3.1

Score:
7.5
Severity:
HIGH
Confidentiality:
None
Integrity:
None
Availability:
None
Attack Vector:
Network
Attack Complexity:
Low
Privileges Required:
None
User Interaction:
None
Scope:
Unchanged

Timeline

  • Vulnerability published

  • Vulnerability Reserved

.