In short
- CVE-2021-39164 is a LOW (CVSS 3.1) vulnerability affecting matrix-synapse, synapse (matrix).
- Chance of exploitation in the next 30 days (EPSS): 1.5%, higher than 73.4% of all vulnerabilities.
- Fix: update to 1.41.1 or later.
Description
Impact
Unauthorised users can access the membership (list of members, with their display names) of a room if they know the ID of the room. The vulnerability is limited to rooms with shared history visibility. Furthermore, the unauthorised user must be using an account on a vulnerable homeserver that is in the room.
Patches
Server administrators should upgrade to 1.41.1 or later.
Workarounds
Administrators of servers that use a reverse proxy could, with potentially unacceptable loss of functionality, block the following endpoints:
/_matrix/client/r0/rooms/{room_id}/members with at query parameter/_matrix/client/unstable/rooms/{room_id}/members with at query parameter
References
n/a
For more information
If you have any questions or comments about this advisory, e-mail us at [email protected].
NVD description
Matrix is an ecosystem for open federated Instant Messaging and Voice over IP. In versions 1.41.0 and prior, unauthorised users can access the membership (list of members, with their display names) of a room if they know the ID of the room. The vulnerability is limited to rooms with `shared` history visibility. Furthermore, the unauthorised user must be using an account on a vulnerable homeserver that is in the room. Server administrators should upgrade to 1.41.1 or later in order to receive the patch. One workaround is available. Administrators of servers that use a reverse proxy could, with potentially unacceptable loss of functionality, block the endpoints: `/_matrix/client/r0/rooms/{room_id}/members` with `at` query parameter, and `/_matrix/client/unstable/rooms/{room_id}/members` with `at` query parameter.
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