CVE-2020-26257 log

Severity Medium
Remote Yes
Type Denial of service
A security issue was found in matrix-synapse before version 1.23.1. A malicious or poorly-implemented homeserver can inject malformed events into a room by specifying a different room id in the path of a /send_join, /send_leave, /invite or /exchange_third_party_invite request. This can lead to a denial of service in which future events will not be correctly sent to other servers over federation. This affects any server which accepts federation requests from untrusted servers.
Group Package Affected Fixed Severity Status Ticket
AVG-1341 matrix-synapse 1.23.0-1 1.24.0-1 Medium Fixed

This issue can be mitigated by limiting access to the federation API to trusted servers (for example by using federation_domain_whitelist).