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Security Advisories: MDE2OlNlY3VyaXR5QWR2aXNvcnlHSFNBLXY5MzYtajhncC05cTNw

Open redirects on some federation and push requests


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.


Issue is resolved by #8821. Further improvements to protect homeservers by default were made in #8870 and #8954.


Requests to internal IP addresses could be blocked at the system or network level.

Source: GitHub Advisory Database
Origin: Unspecified
Severity: Low
Classification: General
Published: over 2 years ago
Updated: 8 months ago

CVSS Score: 3.1
CVSS vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:N/I:L/A:N

Identifiers: GHSA-v936-j8gp-9q3p, CVE-2021-21273

Affected Packages

Versions: < 1.25.0
Fixed in: 1.25.0