CVE-2026-42209
FlashMQ: Division by zero crash when using non-default deferred retained message setting
CVSS Score
6.5
EPSS Score
0.0%
EPSS Percentile
0th
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.
| CWE | CWE-369 |
| Vendor | halfgaar |
| Product | flashmq |
| Published | May 8, 2026 |
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CVSS v3 Breakdown
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H Attack Vector
Network
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High
Affected Versions
halfgaar / FlashMQ
< 1.26.1
References
github.com: https://github.com/halfgaar/FlashMQ/security/advisories/GHSA-2789-vfcg-5922 github.com: https://github.com/halfgaar/FlashMQ/issues/167 github.com: https://github.com/halfgaar/FlashMQ/commit/193b6e7767889511cfa8e933908ea5e6a1077a1f github.com: https://github.com/halfgaar/FlashMQ/releases/tag/v1.26.1