What is CVE-2026-42209?

CVE-2026-42209 is a medium-severity vulnerability in Halfgaar Flashmq, classified under Divide By Zero. CVSS score: 6.5/10. Published 2026-05-08.

How severe is CVE-2026-42209?

Medium severity. CVSS v3 base score is 6.5 out of 10.

Vulnerability in Halfgaar Flashmq

CVE-2026-42209

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_mess…

EPSS: 0.001 (29.9th percentile) — read the EPSS interpretation.

CVSS v3 metric

CVSS v3 base score 6.5 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H.

Affected products

Halfgaar Flashmq — versions < 1.26.1

Weakness classification (CWE)

CWE-369 — Divide By Zero

References

security-advisories@github.com (x_refsource_CONFIRM)
security-advisories@github.com (x_refsource_MISC)
security-advisories@github.com (x_refsource_MISC)
security-advisories@github.com (x_refsource_MISC)

Frequently asked questions

What is CVE-2026-42209?: CVE-2026-42209 is a medium-severity vulnerability in Halfgaar Flashmq, classified under Divide By Zero. CVSS score: 6.5/10. Published 2026-05-08.
How severe is CVE-2026-42209?: Medium severity. CVSS v3 base score is 6.5 out of 10.