CVE-2026-45057: Matrix-Org Matrix-SDK-UI

Medium severity, CVSS 4.9. EPSS: 0.2% chance of exploitation in the next 30 days.

matrix-sdk-ui provides GUI-centric utilities on top of matrix-rust-sdk. The message edit validation logic in the `matrix-sdk-ui` crate prior to 0.17.0 is missing a check: when replacing an encrypted event, the replacement event itself is not required to be encrypted. This enables a malicious homeserver administrators (or actors with equivalent power) to impersonate or spoof messages as if they were sent by a victim user. `matrix-sdk-ui` 0.17.0 fixes the message edit validation logic to align with the algorithm for replacement events[^1] described in the Matrix specification. No known workarounds are available.

Affected products

• Matrix-Org Matrix-SDK-UI: before 0.16.1 (fixed in 0.16.1)

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