Vulnerability 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 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`.
CVSS Score
LOW
Affected Products
| Vendor | Product | Versions |
|---|---|---|
| Matrix | Synapse | < 1.41.1 |
| Fedoraproject | Fedora | 34 |
Related Weaknesses (CWE)
References
- https://github.com/matrix-org/synapse/commit/cb35df940aPatchThird Party Advisory
- https://github.com/matrix-org/synapse/releases/tag/v1.41.1Release NotesThird Party Advisory
- https://github.com/matrix-org/synapse/security/advisories/GHSA-jj53-8fmw-f2w2MitigationThird Party Advisory
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedorapro
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedorapro
- https://github.com/matrix-org/synapse/commit/cb35df940aPatchThird Party Advisory
- https://github.com/matrix-org/synapse/releases/tag/v1.41.1Release NotesThird Party Advisory
- https://github.com/matrix-org/synapse/security/advisories/GHSA-jj53-8fmw-f2w2MitigationThird Party Advisory
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedorapro
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedorapro
FAQ
What is CVE-2021-39163?
CVE-2021-39163 is a vulnerability with a CVSS score of 3.1 (LOW). 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 th...
How severe is CVE-2021-39163?
CVE-2021-39163 has been rated LOW with a CVSS base score of 3.1/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2021-39163?
Check the references section above for vendor advisories and patch information. Affected products include: Matrix Synapse, Fedoraproject Fedora.