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.
Issue is resolved by https://github.com/matrix-org/synapse/pull/8776.
Homeserver administrators could limit access to the federation API to trusted servers (for example via federation_domain_whitelist
).
github.com/matrix-org/synapse/blob/develop/CHANGES.md#synapse-1231-2020-12-09
github.com/matrix-org/synapse/commit/3ce2f303f15f6ac3dc352298972dc6e04d9b7a8b
github.com/matrix-org/synapse/pull/8776
github.com/matrix-org/synapse/security/advisories/GHSA-hxmp-pqch-c8mm
lists.fedoraproject.org/archives/list/[email protected]/message/DBTIU3ZNBFWZ56V4X7JIAD33V5H2GOMC
lists.fedoraproject.org/archives/list/[email protected]/message/QR4MMYZKX5N5GYGH4H5LBUUC5TLAFHI7
nvd.nist.gov/vuln/detail/CVE-2020-26257