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 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 the vulnerable homeserver is in the room and untrusted users are permitted to create groups (communities). 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 to patch the vulnerability. There are two potential workarounds. 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 endpoints `/_matrix/client/r0/groups/{group_id}/rooms` and `/_matrix/client/unstable/groups/{group_id}/rooms`.

The Linux/Unix host has one or more packages installed that are impacted by a vulnerability without a vendor supplied patch available.

  - 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 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 the vulnerable homeserver is in the     room and untrusted users are permitted to create groups (communities). 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 to patch the vulnerability. There are two potential workarounds. 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 endpoints `/_matrix/client/r0/groups/{group_id}/rooms`     and `/_matrix/client/unstable/groups/{group_id}/rooms`. (CVE-2021-39163)

Note that Nessus relies on the presence of the package as reported by the vendor.

Matrix developers report :

This release patches two moderate severity issues which could reveal metadata about private rooms :

- CVE-2021-39164: Enumerating a private room's list of members and their display names.

- CVE-2021-39163: Disclosing a private room's name, avatar, topic, and number of members.

ID	Name	Product	Family	Severity
255962	Linux Distros Unpatched Vulnerability : CVE-2021-39163	Nessus	Misc.	low
153074	FreeBSD : py-matrix-synapse -- several vulnerabilities (a67e358c-0bf6-11ec-875e-901b0e9408dc)	Nessus	FreeBSD Local Security Checks	low

Detections

Analytics

CVE-2021-39163

low

Tenable Plugins

low

low