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Vulnerability · Published Jul 8, 2026 · Assigned by GitHub_M

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

High 7.5

In plain English

A high-severity uncontrolled resource consumption in nats-server from nats-io. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.7% (higher than 55% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)7.5High
Exploit odds (30 days)0.7%top 45.1% of all CVEs
Exploited in the wildNo reportsCISA SSVC: none
Attack toolingNoneno public tooling known

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.

Affected packages & fixed versions

EcosystemPackageFixed inAdvisory
Debian:12nats-serverno fix listedDEBIAN-CVE-2026-58210
Debian:13nats-serverno fix listedDEBIAN-CVE-2026-58210
Debian:14nats-server2.14.3-1DEBIAN-CVE-2026-58210
Ubuntu:24.04:LTSnats-serverno fix listedUBUNTU-CVE-2026-58210
Ubuntu:25.10nats-serverno fix listedUBUNTU-CVE-2026-58210
Ubuntu:26.10nats-serverno fix listedUBUNTU-CVE-2026-58210

Affected products (as reported)

VendorProductVersions
nats-io nats-server < 2.12.12>= 2.14.0-RC.1, < 2.14.3

Weakness: CWE-400 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

References