CVE-2021-39163: Infoleak
First published: Tue Aug 31 2021(Updated: )
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`.
Credit: security-advisories@github.com
| Affected Software | Affected Version | How to fix |
|---|---|---|
| Matrix Synapse | <1.41.1 | |
| Fedoraproject Fedora | =34 | |
| Fedoraproject Fedora | =35 |
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Reference Links
- https://github.com/matrix-org/synapse/commit/cb35df940a
- https://github.com/matrix-org/synapse/releases/tag/v1.41.1
- https://github.com/matrix-org/synapse/security/advisories/GHSA-jj53-8fmw-f2w2
- https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/2VHDEPCZ22GJFMZCWA2XZAGPOEV72POF/
- https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/PXT7ID7DNBRN2TVTETU3SYQHJKEG6PXN/
Frequently Asked Questions
What is CVE-2021-39163?
CVE-2021-39163 is a vulnerability in Matrix Synapse, an ecosystem for open federated Instant Messaging and Voice over IP, where unauthorised users can access certain information of a room if they know the room ID.
What is the severity of CVE-2021-39163?
The severity of CVE-2021-39163 is low, with a CVSS severity score of 3.1.
How can unauthorised users access room information in CVE-2021-39163?
Unauthorised users can access the name, avatar, topic, and number of members of a room if they know the ID of the room.
Which software versions are affected by CVE-2021-39163?
Versions 1.41.0 and prior of Matrix Synapse and Fedora 34 and Fedora 35 are affected by CVE-2021-39163.
How do I fix CVE-2021-39163?
To fix CVE-2021-39163, upgrade to version 1.41.1 of Matrix Synapse.
- collector/nvd-index
- vendor/matrix
- canonical/matrix synapse
- vendor/fedoraproject
- canonical/fedoraproject fedora
- version/fedoraproject fedora/34
- version/fedoraproject fedora/35