CVE-2021-21273

Description

Synapse is a Matrix reference homeserver written in python (pypi package matrix-synapse). Matrix is an ecosystem for open federated Instant Messaging and VoIP. In Synapse before version 1.25.0, 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.

How to fix CVE-2021-21273

To remediate CVE-2021-21273, upgrade the affected package to a fixed version below.

• —upgrade to 1.25.0-1 or later
• —upgrade to 1.25.0 or later
• —upgrade to 30fba6210834a4ecd91badf0c8f3eb278b72e746 or later

Is CVE-2021-21273 being exploited?

Low — EPSS is 0.3%, meaning exploitation activity has not been observed at scale.

Affected packages (3)

• from 0, < 1.25.0-1
• from 0, < 1.25.0
• from 0, < 30fba6210834a4ecd91badf0c8f3eb278b72e746 | from 0, < 1.25.0

CVSS scores

References (9)

• ADVISORYnvd.nist.gov/vuln/detail/CVE-2021-21273
• ADVISORYsecurity-tracker.debian.org/tracker/CVE-2021-21273
• PATCHgithub.com/matrix-org/synapse
• WEBgithub.com/matrix-org/synapse/commit/30fba6210834a4ecd91badf0c8f3eb278b72e746
• WEB