Overview :
Matrix Synapse before 1.5.0 mishandles signature checking on some federation APIs.
Affected Product(s) :
  • Matrix Synapse before 1.5.0
Vulnerability Details :
CVE ID :CVE-2019-18835
 Events sent over /send_join, /send_leave, and /invite may not be correctly signed, or may not come from the expected servers.

Solution :

Update to Matrix Synapse 1.5.0