CVE-2021-29431: SSRF in Sydent due to missing validation of hostnames
Impact
Sydent can be induced to send HTTP GET requests to internal systems, due to lack of parameter validation or IP address blacklisting.
It is not possible to exfiltrate data or control request headers, but it might be possible to use the attack to perform an internal port enumeration.
Patches
Fixed in 9e57334, 8936925, 3d531ed, 0f00412
Workarounds
A potential workaround would be to use a firewall to ensure that Sydent cannot reach internal HTTP resources.
For more information
If you have any questions or comments about this advisory, email us at security@matrix.org.
Other sources
Sydent is a reference Matrix identity server. Sydent can be induced to send HTTP GET requests to internal systems, due to lack of parameter validation or IP address blacklisting. It is not possible to exfiltrate data or control request headers, but it might be possible to use the attack to perform an internal port enumeration. This issue has been addressed in in 9e57334, 8936925, 3d531ed, 0f00412. A potential workaround would be to use a firewall to ensure that Sydent cannot reach internal HTTP resources.
Affected Software
Remediation
Event History
Frequently Asked Questions
What is CVE-2021-29431?
CVE-2021-29431 is a vulnerability in the Matrix Sydent identity server that allows for the sending of HTTP GET requests to internal systems.
What is the severity of CVE-2021-29431?
CVE-2021-29431 has a severity rating of high with a score of 6.5.
How does CVE-2021-29431 affect Matrix Sydent?
CVE-2021-29431 affects Matrix Sydent versions up to and excluding 2.3.0.
Is it possible to exfiltrate data or control request headers with CVE-2021-29431?
No, it is not possible to exfiltrate data or control request headers with CVE-2021-29431.
How can I fix CVE-2021-29431?
To fix CVE-2021-29431, update to a version of Matrix Sydent that includes the necessary patches.