CVE-2026-42209
MEDIUMFlashMQ: Division by zero crash when using non-default deferred retained message setting
Title source: cnaDescription
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.
References (4)
Core 4
Core References
X_Refsource_Confirm x_refsource_confirm
https://github.com/halfgaar/FlashMQ/security/advisories/GHSA-2789-vfcg-5922
X_Refsource_Misc x_refsource_misc
https://github.com/halfgaar/FlashMQ/issues/167
X_Refsource_Misc x_refsource_misc
https://github.com/halfgaar/FlashMQ/commit/193b6e7767889511cfa8e933908ea5e6a1077a1f
X_Refsource_Misc x_refsource_misc
https://github.com/halfgaar/FlashMQ/releases/tag/v1.26.1
Scores
CVSS v3
6.5
EPSS
0.0036
EPSS Percentile
27.2%
Attack Vector
NETWORK
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
CISA SSVC
Vulnrichment
Exploitation
poc
Automatable
no
Technical Impact
partial
Details
CWE
CWE-369
Status
published
Products (1)
halfgaar/FlashMQ
< 1.26.1
Published
May 08, 2026
Tracked Since
May 09, 2026