matrix-sdk-crypto is a no-network-IO implementation of a state machine that handles end-to-end encryption for Matrix clients. Starting in version 0.12.0 and prior to version 0.17.0, the matrix-sdk-crypto crate was missing a check for the user ID when decrypting an Olm-encrypted event containing the `sender_device_keys` property. This could be exploited to forge an encrypted to-device event, but only if the attacker colludes with the homeserver operator.
This issue is fixed in matrix-sdk-crypto 0.17.0. There are no known workarounds for the issue.
Attack Parameters
Attack Vector
Network
Can be exploited remotely
Attack Complexity
Low
Easy to exploit
Attack Requirements
None
No additional conditions
Privileges Required
High
Admin privileges needed
User Interaction
None
No user interaction needed
Impact Assessment
Confidentiality
None
No data leak
Integrity
High
Complete data modification
Availability
None
No disruption
CVSS Vector v4.0
Weakness Type (CWE)
References 4
https://github.com/matrix-org/matrix-rust-sdk/pull/6553
security-advisories@github.com
https://github.com/matrix-org/matrix-rust-sdk/releases/tag/matrix-sdk-0.16.1
security-advisories@github.com
https://github.com/matrix-org/matrix-rust-sdk/security/advisories/GHSA-wfq4-36m…
security-advisories@github.com
https://rustsec.org/advisories/RUSTSEC-2026-0159.html
security-advisories@github.com