CVE-2026-58214: Linuxfoundation Nats-Server

Medium severity, CVSS 4.3. EPSS: 0.3% chance of exploitation in the next 30 days.

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 authenticated MQTT client could subscribe to the internal $MQTT.deliver.pubrel subject family, bypassing configured subscribe permissions and exposing MQTT QoS2 protocol metadata for sessions in the account. This issue is fixed in versions 2.14.3 and 2.12.12.

Affected products

• Linuxfoundation Nats-Server: before 2.12.12 (fixed in 2.12.12); from 2.14.0, before 2.14.3 (fixed in 2.14.3)

Published 2026-07-08. Last modified 2026-07-13.