CVE-2026-45056: Matrix-Org Matrix-Rust-SDK

Medium severity, CVSS 6.9. EPSS: 0.3% chance of exploitation in the next 30 days.

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.

Affected products

• Matrix-Org Matrix-Rust-SDK: from 0.12.0, before 0.16.1 (fixed in 0.16.1)

Published 2026-09-11. Last modified 2026-09-30.