CVE-2026-42209: CWE-369: Divide By Zero in halfgaar FlashMQ
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.
AI Analysis
Technical Summary
FlashMQ, an MQTT broker designed for multi-CPU environments, contains a divide-by-zero vulnerability (CWE-369) in versions before 1.26.1. The flaw occurs when both set_retained_message_defer_timeout and set_retained_message_defer_timeout_spread are configured to non-default values. A remote client with retained publish permission can exploit this to crash the broker, causing denial of service. Exploitation requires either anonymous retained publishing enabled or valid publish permissions. The issue is addressed in FlashMQ version 1.26.1.
Potential Impact
Successful exploitation causes a denial of service by crashing the FlashMQ broker, disrupting MQTT messaging services. There is no impact on confidentiality or integrity reported. The vulnerability requires either anonymous retained publishing enabled or valid publish permissions, limiting the attack surface.
Mitigation Recommendations
A fix is available in FlashMQ version 1.26.1. Users should upgrade to this version or later to remediate the vulnerability. No other official mitigations or temporary fixes are documented. Patch status is confirmed by the vendor advisory stating the issue is fixed in 1.26.1.
CVE-2026-42209: CWE-369: Divide By Zero in halfgaar FlashMQ
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.
CVSS v3.1
Score 6.5medium
Affected software
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Weaknesses
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
FlashMQ, an MQTT broker designed for multi-CPU environments, contains a divide-by-zero vulnerability (CWE-369) in versions before 1.26.1. The flaw occurs when both set_retained_message_defer_timeout and set_retained_message_defer_timeout_spread are configured to non-default values. A remote client with retained publish permission can exploit this to crash the broker, causing denial of service. Exploitation requires either anonymous retained publishing enabled or valid publish permissions. The issue is addressed in FlashMQ version 1.26.1.
Potential Impact
Successful exploitation causes a denial of service by crashing the FlashMQ broker, disrupting MQTT messaging services. There is no impact on confidentiality or integrity reported. The vulnerability requires either anonymous retained publishing enabled or valid publish permissions, limiting the attack surface.
Mitigation Recommendations
A fix is available in FlashMQ version 1.26.1. Users should upgrade to this version or later to remediate the vulnerability. No other official mitigations or temporary fixes are documented. Patch status is confirmed by the vendor advisory stating the issue is fixed in 1.26.1.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- GitHub_M
- Date Reserved
- 2026-04-25T05:04:37.028Z
- Cvss Version
- 3.1
- State
- PUBLISHED
- Remediation Level
- null
Threat ID: 69fe5e60cbff5d8610336e76
Added to database: 05/08/2026, 22:06:24 UTC
Last enriched: 05/16/2026, 10:53:22 UTC
Last updated: 07/31/2026, 19:22:58 UTC
Views: 152
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