Matrix Rust SDK: Sender-binding gaps in to-device and room-key attribution

### Impact The `matrix-sdk-crypto` crate before 0.16.1 is missing a check for the sender's user ID when decrypting an Olm-encrypted to-device message containing the `sender_device_keys` property. This could be exploited to spoof the sender of an encrypted to-device message, but only if the attacker colludes with (or is) the homeserver operator. ### Patches This issue is fixed in `matrix-sdk-crypto` 0.16.1. ### Workarounds There are no known workarounds for the issue. ### References This issue was fixed in https://github.com/matrix-org/matrix-rust-sdk/pull/6553. ### For more information If you have any questions or comments about this advisory, please email us at [security at matrix.org](mailto:[email protected]).

Source published

4 Jun 2026 14:47:05 UTC

Source modified

4 Jun 2026 15:00:08 UTC

Observed here

24 Oct 2026 13:19:54 UTC

Source terms

GitHub Advisory Database · CC-BY-4.0

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This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: osv · GitHub Advisory Database · CC-BY-4.0. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS_V4 · CVSS:4.0/AV:N/AC:L/AT:N/PR:H/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N

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