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Fencer Vulns
medium 4.3

CVE-2026-58209 json

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

published 2026-07-08 4 mo ago modified 2026-10-25 14 d ago also BIT-nats-2026-58209 , EUVD-2026-42347 , GHSA-7qmq-8cc4-hxwg , JLSEC-2026-1146

cvss
4.3
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.3%
EPSS 0.3% chance of exploitation in 30 days, percentile 27%
public exploits
0
none known

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.

Patch / fix

  • bitnami nats 2.12.12, 2.14.3
  • julia nats_server_jll 2.14.3+0
  • linuxfoundation nats-server 2.12.12, 2.14.3
  • nats nats_server 2.12.12, 2.14.3
  • nats nats_streaming_server 2.12.12, 2.14.3
  • nats-server Debian 14 2.14.3-1

debian advisories DEBIAN-CVE-2026-58209

  • nats-server2.12 hummingbird 1 2.12.12-1.hum1
  • nats-server2.14 hummingbird 1 2.14.3-1.hum1

red hat advisories RHSA-2026:36017RHSA-2026:36016

  • telegraf Azure Linux 3.0 1.31.0-27

azure linux advisories AZL-92256

Azure Linux vulnerability data, Copyright (c) Microsoft Corporation, from https://github.com/microsoft/AzureLinuxVulnerabilityData via OSV, under the MIT licence; changed: normalised to fixed package versions per release. MIT

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-58209 updated cvss 4.3

nats-server: NATS Server: Information disclosure due to inconsistent MQTT topic rechecking

  • Red Hat Hardened Images nats-server2.14 2.14.3-1.hum1, nats-server2.12 2.12.12-1.hum1
    fixed: vendor fix RHSA-2026:36017

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
none
Automatable
no
Technical impact
partial
Assessed
4 mo ago

Exploit prediction

0.34% chance of exploitation in the next 30 days, higher than 27% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 4.3 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N
OSV 3.1 4.3 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N

Affected packages

ecosystem package affected fixed in
bitnami nats
<2.12.12
>=2.14.0, <2.14.3
2.12.12
2.14.3
julia nats_server_jll
<2.14.3+0
2.14.3+0

Affected products

  • nats-io nats-server

Classification

Weakness

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.