CVE-2026-58214
NATS Server: MQTT subscribe ACL bypass via $MQTT.deliver.pubrel prefix (incomplete fix for CVE-2026-33217)
CVSS Score
4.3
EPSS Score
0.4%
EPSS Percentile
29th
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.
| CWE | CWE-863 |
| Vendor | nats-io |
| Product | nats-server |
| Published | Jul 8, 2026 |
| Last Updated | Jul 9, 2026 |
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CVSS v3 Breakdown
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N Attack Vector
Network
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
Low
Integrity
None
Availability
None
Affected Versions
nats-io / nats-server
< 2.12.12 >= 2.14.0-RC.1, < 2.14.3
References
github.com: https://github.com/nats-io/nats-server/security/advisories/GHSA-4g68-3pwx-5vfj github.com: https://github.com/nats-io/nats-server/commit/297b166be60fe13144084eed4b25201ead03204a github.com: https://github.com/nats-io/nats-server/commit/34b09657bb596d5f850eaa5cfc97ea6b2f989a97 github.com: https://github.com/nats-io/nats-server/releases/tag/v2.12.12 github.com: https://github.com/nats-io/nats-server/releases/tag/v2.14.3