CVE-2026-46411: FlashMQ: Client can trigger uncaught exception on FlashMQ 1.26.1 and older

Severity: medium (CVSS 6.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.3% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-06-10 · updated 2026-07-23
Weakness: CWE-248

Description

FlashMQ is a MQTT broker/server, designed for multi-CPU environments. Prior to version 1.26.2, authorized clients have the ability to exceed the permitted over-commit of their write buffer and triggering an internal safe-guard exception. This exception was in a path that was not catchable, and therefore causes a server abort. This issue has been patched in version 1.26.2.

Affected products

halfgaar FlashMQ: before 1.26.2

References

https://github.com/halfgaar/FlashMQ/commit/29e08f7b97b6e3f96db923c2b6a260c47b49c195
https://github.com/halfgaar/FlashMQ/releases/tag/v1.26.2
https://github.com/halfgaar/FlashMQ/security/advisories/GHSA-g35r-265r-rxrh

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