CVE-2026-46411 FlashMQ: Client can trigger uncaught exception on FlashMQ 1.26.1 and older
Authorized clients can crash the FlashMQ MQTT broker by exceeding write buffer limits, causing a server abort.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-46411?
CVE-2026-46411 is a medium-severity denial of service vulnerability in halfgaar FlashMQ, published on 9 Jun 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Official 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.
Weakness: CWE-248
Which versions are affected by CVE-2026-46411?
How do I fix CVE-2026-46411?
No fix has been published for CVE-2026-46411 yet. Limit exposure of the affected software until one is available.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-46411 being exploited?
There is no known exploitation of CVE-2026-46411 in the wild and no public exploit code.
Sources
Also known as GHSA-g35r-265r-rxrh.