Is CVE-2026-42209 actively exploited?

No active exploitation of CVE-2026-42209 has been confirmed so far. Continue monitoring, as exploit status can change.

Can CVE-2026-42209 be exploited remotely?

Yes. CVE-2026-42209 is exploitable remotely over the network (CVSS attack vector: Network).

What is the CVSS score of CVE-2026-42209?

CVE-2026-42209 has a CVSS score of 6.5 (MEDIUM).

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MEDIUM

CVE-2026-42209

CWE-369Published: May 8, 2026· Updated: May 13, 2026

6.5

CVSS v3.1

EPSS:0.11%probability of exploitation in 30 daysPercentile:29.8th

Official Description

FlashMQ is a MQTT broker/server, designed for multi-CPU environments. Prior to version 1.26.1, a remote client with retained publish permission can crash the FlashMQ broker when both set_retained_message_defer_timeout and set_retained_message_defer_timeout_spread are configured to non-default values, resulting in denial of service. If anonymous retained publishing is allowed, no authentication is required; otherwise, the attacker needs the corresponding publish permission. This issue has been patched in version 1.26.1.

NVD Source

Technical Analysis

CVE-2026-42209 can be exploited remotely over the network without requiring physical or adjacent access, significantly expanding the attack surface for threat actors.

Exploitation requires low privileges, which limits the exposure to scenarios where an attacker has already gained initial access.

A successful exploit results in availability disruption (denial of service), with a CVSS base score of 6.5.