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Vulnerability · Published Jul 8, 2026 · Assigned by GitHub_M

CVE-2026-58254NATS Server: Incomplete fix for CVE-2026-33249: Leaf node connections bypass Nats-Trace-Dest permission check

Medium 5.3

In plain English

A medium-severity incorrect authorization 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 0.3% (higher than 24% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 4.0)5.3Medium
Exploit odds (30 days)0.3%top 76.2% 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 2.12.8, message trace destination checks were applied to ordinary client connections but not consistently to messages arriving through leafnode connections, allowing a leafnode operator to send trace events to subjects that would not otherwise be permitted and to use trace-only behavior to prevent normal delivery or storage of affected messages. This issue is fixed in versions 2.14.3 and 2.12.8.

Affected packages & fixed versions

EcosystemPackageFixed inAdvisory
Debian:12nats-serverno fix listedDEBIAN-CVE-2026-58254
Debian:13nats-serverno fix listedDEBIAN-CVE-2026-58254
Debian:14nats-server2.14.3-1DEBIAN-CVE-2026-58254
Ubuntu:24.04:LTSnats-serverno fix listedUBUNTU-CVE-2026-58254
Ubuntu:25.10nats-serverno fix listedUBUNTU-CVE-2026-58254
Ubuntu:26.10nats-serverno fix listedUBUNTU-CVE-2026-58254

Affected products (as reported)

VendorProductVersions
nats-io nats-server < 2.12.8>= 2.14.0-RC.1, < 2.14.3

Weakness: CWE-863 · Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:L/VI:L/VA:L/SC:N/SI:N/SA:N

References