Unauthorised users can access the name, avatar, topic and number of members of a room if they know the ID of the room. This vulnerability is limited to homeservers where:
By default, only homeserver administrators can create groups. However, homeserver administrators can already access this information in the database or using the admin API. As a result, only homeservers where the configuration setting enable_group_creation
has been set to true
are impacted.
Server administrators should upgrade to 1.41.1 or higher.
Server administrators can set enable_group_creation
to false
in their homeserver configuration (this is the default value) to prevent creation of groups by non-administrators.
Administrators that are using a reverse proxy could, with partial loss of group functionality, block the following endpoints:
/_matrix/client/r0/groups/{group_id}/rooms
/_matrix/client/unstable/groups/{group_id}/rooms
n/a
If you have any questions or comments about this advisory, e-mail us at [email protected].
github.com/matrix-org/synapse
github.com/matrix-org/synapse/commit/cb35df940a
github.com/matrix-org/synapse/releases/tag/v1.41.1
github.com/matrix-org/synapse/security/advisories/GHSA-jj53-8fmw-f2w2
lists.fedoraproject.org/archives/list/[email protected]/message/2VHDEPCZ22GJFMZCWA2XZAGPOEV72POF
lists.fedoraproject.org/archives/list/[email protected]/message/PXT7ID7DNBRN2TVTETU3SYQHJKEG6PXN
nvd.nist.gov/vuln/detail/CVE-2021-39163