CVE-2026-42209

FlashMQ: Division by zero crash when using non-default deferred retained message setting

Published May 8, 2026 CVSS 3.1 · 6.5 Medium EPSS < 1% KEV · Not listed
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.

Remediation

No solution or workaround provided in the CVE record

Tracking

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Advisories

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History
Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'poc', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Type Values Removed Values Added
First Time appeared Halfgaar
Halfgaar flashmq
Vendors & Products Halfgaar
Halfgaar flashmq
Type Values Removed Values Added
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.
Title FlashMQ: Division by zero crash when using non-default deferred retained message setting
Weaknesses CWE-369
References
Metrics cvssV3_1

{'score': 6.5, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H'}

Weaknesses

Sources

Status
PUBLISHED
Assigner
GitHub_M
Published
Updated
May 11, 2026, 3:59 PM
Reserved
Apr 25, 2026, 5:04 AM
Status
Deferred
Published
May 8, 2026, 10:16 PM
Modified
Oct 26, 2026, 6:10 PM