Synapse 1.41.1 (2021-08-31)

===========================

Due to the two security issues highlighted below, server administrators are encouraged to update Synapse. We are not aware of these vulnerabilities being exploited in the wild.

Security advisory
-----------------

The following issues are fixed in v1.41.1.

- **[GHSA-3x4c-pq33-4w3q](https://github.com/matrix-org/synapse/security/advisories/GHSA-3x4c-pq33-4w3q) / [CVE-2021-39164](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2021-39164): Enumerating a private room's list of members and their display names.**

  If an unauthorized user both knows the Room ID of a private room *and* that room's history visibility is set to `shared`, then they may be able to enumerate the room's members, including their display names.

  The unauthorized user must be on the same homeserver as a user who is a member of the target room.

  Fixed by [52c7a51cf](https://github.com/matrix-org/synapse/commit/52c7a51cf).

- **[GHSA-jj53-8fmw-f2w2](https://github.com/matrix-org/synapse/security/advisories/GHSA-jj53-8fmw-f2w2) / [CVE-2021-39163](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2021-39163): Disclosing a private room's name, avatar, topic, and number of members.**

  If an unauthorized user knows the Room ID of a private room, then its name, avatar, topic, and number of members may be disclosed through Group / Community features.

  The unauthorized user must be on the same homeserver as a user who is a member of the target room, and their homeserver must allow non-administrators to create groups (`enable_group_creation` in the Synapse configuration; off by default).

  Fixed by [cb35df940a](https://github.com/matrix-org/synapse/commit/cb35df940a), [\#10723](https://github.com/matrix-org/synapse/issues/10723).

Bugfixes
--------

- Fix a regression introduced in Synapse 1.41 which broke email transmission on systems using older versions of the Twisted library. ([\#10713](https://github.com/matrix-org/synapse/issues/10713))