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GHSA-3h7q-rfh9-xm4v
No affected components available
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.
The vulnerability can be exploited over the network without needing physical access. It is easy for an attacker to exploit this vulnerability. An attacker needs basic access or low-level privileges. No user interaction is needed for the attacker to exploit this vulnerability. The impact is confined to the system where the vulnerability exists. There is a high impact on the availability of the system.
Exploitation attempts have been detected. Elevated vigilance and prompt remediation are advised.
The exploit probability is very low. The vulnerability is unlikely to be exploited in the next 30 days.
We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.
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