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TI-2026-41919 Aliases CVE-2026-58209

NATS Server: MQTT retained and QoS replay bypass subscribe deny filters

Priority LOW 20CWE-863Published · Updated

Key facts

Attack vector
Network
Privileges required
Low
User interaction
None
Attack complexity
Low
Impact type
Security bypass
Confidentiality · integrity · availability
Low · None · None
Fix status
Fixed

Attack profile from CVSS 3.1 · CNA. Fix status from CNA and Red Hat. Impact type from CWE-863.

Summary

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, MQTT retained message delivery and QoS1+ durable replay could deliver messages whose original topics matched a subscriber configured subscribe deny rule because these delivery paths did not consistently recheck the concrete original topic before sending the MQTT PUBLISH to the subscriber. This issue is fixed in versions 2.14.3 and 2.12.12.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.00342 27th percentileScored 2026-11-07
Fix Fixed nats-server (nats-io): 2.12.12, 2.14.3Red Hat: 2 advisories

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
None
Automatable
No
Technical impact
Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
backstagenats-serverbefore 2.12.12; 2.14.0-RC.1 to before 2.14.32.12.12, 2.14.3Patch availableCNA
  • nats-server Vendorbackstage Affected before 2.12.12; 2.14.0-RC.1 to before 2.14.3 Fixed in 2.12.12, 2.14.3 Patch available CNA

CPE configurations NVD · 1

CPEVersionsRoleVendor
cpe:2.3:a:linuxfoundation:nats-server:*:*:*:*:*:*:*:*before 2.12.12; 2.14.0 to before 2.14.3Vulnerablebackstage
  • cpe:2.3:a:linuxfoundation:nats-server:*:*:*:*:*:*:*:* Versions before 2.12.12; 2.14.0 to before 2.14.3 Vulnerable ·backstage

Remediation

  • Fix · CNA nats-server (nats-io) Fixed in 2.12.12, 2.14.3

Red Hat 2 advisories

  • RHSA-2026:36017 Released 2026-07-06 · Red Hat rating Important
    Red Hat Hardened Images RPMs bug fix and enhancement update
    • Red Hat Hardened Images nats-server2-12-main@aarch64, nats-server2-12-main@src, nats-server2-12-main@x86_64
  • RHSA-2026:36016 Released 2026-07-06 · Red Hat rating Important
    Red Hat Hardened Images RPMs bug fix and enhancement update
    • Red Hat Hardened Images nats-server2-14-main@aarch64, nats-server2-14-main@src, nats-server2-14-main@x86_64

Vendor assessments

Red Hat

Red Hat rating: Moderate. Red Hat's page for this CVE →

ProductStatusPlan or fix
Red Hat Hardened ImagesFixed RHSA-2026:36016, RHSA-2026:36017

Timeline

  1. 2026-10-02 Threatist record created from CVE-2026-58209

References

Patch 2

Advisory 1

Other 2

  • TI-2026-22233 NATS: Pre-auth remote server crash via WebSocket frame length overflow in wsRead CVSS 3.1HIGH 7.5
  • TI-2022-11116 NATS nats-server 2.2.0 through 2.7.4 allows directory traversal because of an unintended… CVSS 3.1CRITICAL 9.8
  • TI-2020-16319 The JWT library in NATS nats-server before 2.1.9 has Incorrect Access Control because of… CVSS 3.1CRITICAL 9.8
  • TI-2026-25637 NATS has MQTT plaintext password disclosure CVSS 3.1HIGH 8.6
  • TI-2022-08320 NATS nats-server before 2.7.2 has Incorrect Access Control. CVSS 3.1HIGH 8.8
  • TI-2026-41950 NATS Server: Pre-auth server crash via double INFO in leafnode handshake CVSS 3.1HIGH 7.5
See all 35 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences