AIKIDO-2026-304894
matrix-synapse is vulnerable to Spoofing
75
High Risk
This Affects:
matrix-synapseTL;DR
Synapse accepts to-device messages from remote homeservers without verifying that the message sender belongs to the originating server. A malicious federated homeserver can spoof the sender field so that a to-device message appears to have come from a different homeserver. This allows impersonation of users on other servers in to-device traffic. The fix validates the message origin against the claimed sender.
Who does this affect?
You are affected if you are using a version that falls within the vulnerable range and your homeserver participates in open federation.
Background info
matrix-synapse is vulnerable to Spoofing in versions 0.0.1 - 1.157.1.
How to fix this
Upgrade the matrix-synapse library to the patch version.
Are You Affected?
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