CVE-2018-12423: Matrix Synapse

High severity, CVSS 7.5. EPSS: 1.8% chance of exploitation in the next 30 days.

In Synapse before 0.31.2, unauthorised users can hijack rooms when there is no m.room.power_levels event in force.

Affected products

• Matrix Synapse: before 0.31.2 (fixed in 0.31.2)

Published 2018-06-14. Last modified 2026-06-17.