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GHSA-v936-j8gp-9q3p

LowCVSS 3.1 / 10
Published Feb 26, 2021·Last modified Mar 13, 2026
Affected Components(0)

No affected components available

Description

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.

Risk Scores
Base Score
3.1

The vulnerability can be exploited over the network without needing physical access. It is difficult for an attacker to exploit this vulnerability and may require special conditions. An attacker does not need any special privileges or access rights. The attacker needs the user to perform some action, like clicking a link. The impact is confined to the system where the vulnerability exists. There is a low impact on the integrity of the data.

Threat Intelligence
2.9

Limited exploitation activity has been observed. Close monitoring and planned remediation are recommended.

EPSS
1.81%

The exploit probability is very low. The vulnerability is unlikely to be exploited in the next 30 days.

Exploit
Not available

We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.

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Low severity
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