CVE-2024-31208: Synapse's V2 state resolution weakness allows DoS from remote room members
Impact
A remote Matrix user with malicious intent, sharing a room with Synapse instances before 1.105.1, can dispatch specially crafted events to exploit a weakness in how the auth chain cover index is calculated. This can induce high CPU consumption and accumulate excessive data in the database of such instances, resulting in a denial of service.
Servers in private federations, or those that do not federate, are not affected.
Patches
Server administrators should upgrade to 1.105.1 or later.
Workarounds
One can: - ban the malicious users or ACL block servers from the rooms; and/or - leave the room and purge the room using the admin API
For more information
If you have any questions or comments about this advisory, please email us at security AT element.io.
Other sources
Synapse is an open-source Matrix homeserver. A remote Matrix user with malicious intent, sharing a room with Synapse instances before 1.105.1, can dispatch specially crafted events to exploit a weakness in the V2 state resolution algorithm. This can induce high CPU consumption and accumulate excessive data in the database of such instances, resulting in a denial of service. Servers in private federations, or those that do not federate, are not affected. Server administrators should upgrade to 1.105.1 or later. Some workarounds are available. One can ban the malicious users or ACL block servers from the rooms and/or leave the room and purge the room using the admin API.
— NVD
Affected Software
Remediation
Event History
Frequently Asked Questions
What is the severity of CVE-2024-31208?
CVE-2024-31208 has a moderate severity as it can lead to high CPU consumption affecting system performance.
How do I fix CVE-2024-31208?
To mitigate CVE-2024-31208, upgrade matrix-synapse to version 1.105.1 or later.
Who is affected by CVE-2024-31208?
CVE-2024-31208 affects Synapse instances running versions prior to 1.105.1.
What type of vulnerability is CVE-2024-31208?
CVE-2024-31208 is a remote code execution vulnerability that can lead to resource exhaustion.
Can CVE-2024-31208 be exploited remotely?
Yes, CVE-2024-31208 can be exploited by remote Matrix users sharing a room with vulnerable Synapse instances.