NATS Server: MQTT subscribe ACL bypass via $MQTT.deliver.pubrel prefix (incomplete fix for CVE-2026-33217)

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Summary

CVECVE-2026-58214
StatePUBLISHED
AssignerGitHub_M
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-07-08 20:16:54 UTC
Updated2026-07-08 20:16:54 UTC
DescriptionNATS 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.

Risk And Classification

Primary CVSS: v3.1 4.3 MEDIUM from [email protected]

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N

Problem Types: CWE-863 | CWE-863 CWE-863: Incorrect Authorization

VersionSourceTypeScoreSeverityVector
3.1[email protected]Secondary4.3MEDIUMCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N
3.1CNADECLARED4.3MEDIUMCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
Low
Integrity
None
Availability
None

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Nats-io Nats-server affected < 2.12.12 Not specified
CNA Nats-io Nats-server affected >= 2.14.0-RC.1, < 2.14.3 Not specified

References

ReferenceSourceLinkTags
github.com/nats-io/nats-server/releases/tag/v2.12.12 [email protected] github.com
github.com/nats-io/nats-server/security/advisories/GHSA-4g68-3pwx-5vfj [email protected] github.com
github.com/nats-io/nats-server/commit/34b09657bb596d5f850eaa5cfc97ea6b2f... [email protected] github.com
github.com/nats-io/nats-server/commit/297b166be60fe13144084eed4b25201ead... [email protected] github.com
github.com/nats-io/nats-server/releases/tag/v2.14.3 [email protected] github.com
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