CSIRTS // UNIFIED SECURITY ADVISORY FEEDSYS ● ONLINE · POWERED BY INTELFUSIONS.COM

← Back to feed

CVE-2026-58209: NATS Server: MQTT retained and QoS replay bypass subscribe deny filters

mediumCVSS 4.3CVE-2026-58209

CSIRTS triage

vendor: NATSproduct: NATS ServerAuthentication bypass
What
This vulnerability allows for bypassing subscribe deny filters for MQTT retained and QoS replay.
Who is affected
Deployments of NATS Server are affected.
Urgency
Remediation is necessary due to the medium severity of the vulnerability.
Action
Update to the latest version of NATS Server to mitigate this issue.

AI-assisted analysis generated from the source advisory — verify against the original.

⚡ Watch NATS Server

Get an email when a new NATS Server advisory drops — max one per day, one-click unsubscribe.

Details

Source
Microsoft Security Response Center (INTL · vendor-psirt · site)
Severity
medium — CVSS 4.3
Published
2026-07-02
Exploitation
Not in CISA KEV at last sync

Original advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-58209

Exploitation outlook

EPSS (FIRST.org) estimates each CVE’s probability of exploitation in the next 30 days — here is the CSIRTS.com read on those numbers.

Referenced CVEs

CVECSIRTS overviewExternal
CVE-2026-58209coverage & exploitation statusNVD · CVE.org

Same CVEs, other sources

How other CERTs, PSIRTs and databases cover the vulnerabilities in this advisory.

Recent advisories for NATS Server

A cluster of recent advisories against the same product widens the attack surface — attackers routinely chain freshly published CVEs on one product, so review these together.

More from Microsoft Security Response Center