CVE-2026-42209: CWE-369: Divide By Zero in halfgaar FlashMQ
CVE-2026-42209 is a medium severity vulnerability in halfgaar FlashMQ versions prior to 1. 26. 1. It involves a divide-by-zero error that can be triggered remotely by a client with retained publish permission when specific configuration parameters are set to non-default values. This results in a denial of service by crashing the FlashMQ broker. If anonymous retained publishing is enabled, no authentication is required to exploit this issue; otherwise, the attacker must have publish permission. The vulnerability has been fixed 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 trigger this condition 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 according to the CVSS vector. The vulnerability requires either anonymous retained publishing or valid publish permissions, limiting the attack surface.
Mitigation Recommendations
Upgrade FlashMQ to version 1.26.1 or later, where this vulnerability is patched. Until upgrade, review and consider disabling anonymous retained publishing and carefully manage publish permissions to reduce exposure. Patch status is confirmed by the vendor advisory stating the issue is fixed in version 1.26.1.
CVE-2026-42209: CWE-369: Divide By Zero in halfgaar FlashMQ
Description
CVE-2026-42209 is a medium severity vulnerability in halfgaar FlashMQ versions prior to 1. 26. 1. It involves a divide-by-zero error that can be triggered remotely by a client with retained publish permission when specific configuration parameters are set to non-default values. This results in a denial of service by crashing the FlashMQ broker. If anonymous retained publishing is enabled, no authentication is required to exploit this issue; otherwise, the attacker must have publish permission. The vulnerability has been fixed in version 1. 26. 1.
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 trigger this condition 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 according to the CVSS vector. The vulnerability requires either anonymous retained publishing or valid publish permissions, limiting the attack surface.
Mitigation Recommendations
Upgrade FlashMQ to version 1.26.1 or later, where this vulnerability is patched. Until upgrade, review and consider disabling anonymous retained publishing and carefully manage publish permissions to reduce exposure. Patch status is confirmed by the vendor advisory stating the issue is fixed in version 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: 5/8/2026, 10:06:24 PM
Last enriched: 5/8/2026, 10:21:56 PM
Last updated: 5/9/2026, 1:22:36 AM
Views: 5
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