VULNERABILITY INTELLIGENCE

CVE-2021-39164

CVSS score3.1 LOW
EPSS probability1.45%
CISA KEVNot currently listed
Published2021-08-31
Last modified2026-06-17
CVSS vectorCVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:L/I:N/A:N

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.

Weakness classification

  • CWE-200: Exposure of Sensitive Information to an Unauthorized Actor
  • CWE-863: Incorrect Authorization

Primary references