CVE-2021-21273Low· 3.1▾ SunlitOpen redirects on some federation and push requests
▾ Sunlit zone — Low / medium · no exploitation signal
impact 17.1 · likelihood 0.4 · exploitation 0
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Exploit-prediction probability, daily snapshots since Jul 8.
Disclosure to exploitation, from the record and what we observed since indexing it.
Disclosed via OSV
Last analysed / modified upstream
1.8%
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.
matrix-synapse < 1.25.0Upgrade to a patched release:
matrix-synapse 1.25.0Connected by shared product, vendor, weakness, or advisory.
CVE-2021-21274Medium· 4.3Denial of service attack via .well-known lookups
CVE-2021-29471Low· 3.7Denial of service attack via push rule patterns in matrix-synapse
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CVE-2021-21393Medium· 5.3Denial of service (via resource exhaustion) due to improper input validation on groups/communities endpoints
CVE-2021-21333Medium· 6.1HTML injection in email and account expiry notifications
CVE-2021-21392Medium· 6.3Open redirect via transitional IPv6 addresses on dual-stack networks