medium3.1

CVE-2021-21273

Open redirects on some federation and push requests

Impact

### Impact Requests to user provided domains were not restricted to external IP addresses when calculating the key validity for third-party invite events and sending push notifications. This could cause Synapse to make requests to internal infrastructure. The type of request was not controlled by the user, although limited modification of request bodies was possible. For the most thorough protection server administrators should remove the deprecated `federation_ip_range_blacklist` from their settings after upgrading to Synapse v1.25.0 which will result in Synapse using the improved default IP address restrictions. See the new `ip_range_blacklist` and `ip_range_whitelist` settings if more specific control is necessary. ### Patches Issue is resolved by #8821. Further improvements to protect homeservers by default were made in #8870 and #8954. ### Workarounds Requests to internal IP addresses could be blocked at the system or network level.

Affected packages

Ecosystem	Package	Affected	Fixed in
pip	`matrix-synapse`	< 1.25.0	1.25.0

Affected products

Vendor	Product	Affected versions
Matrix	Synapse	before 1.25.0
Fedoraproject	Fedora	Version 34

Weakness classification

CWE-601

Impact

Affected packages

Affected products

Weakness classification

References