CVE-2021-39164Low· 3.1▾ SunlitImproper authorisation of members discloses room membership to non-members
▾ Sunlit zone — Low / medium · no exploitation signal
impact 17.1 · likelihood 0.3 · exploitation 0
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Exploit-prediction probability, daily snapshots since Jul 8.
Disclosure to exploitation, from the record and what we observed since indexing it.
Disclosed via OSV
Last analysed / modified upstream
1.5%
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.
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 parametern/a
If you have any questions or comments about this advisory, e-mail us at [email protected].
matrix-synapse < 1.41.1Upgrade to a patched release:
matrix-synapse 1.41.1Connected by shared product, vendor, weakness, or advisory.
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