CVE-2026-45057 matrix-sdk-ui: Incomplete edit validation
A malicious homeserver can spoof encrypted messages by bypassing edit validation, allowing impersonation of users in Matrix clients.
- Exploited in the wild
- Not known
- Login needed
- An administrator
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-45057?
CVE-2026-45057 is a medium-severity missing authorization vulnerability in matrix-org matrix-sdk-ui, published on 11 Sep 2026. An attacker needs administrator access to exploit it, with no action from the victim.
Official description
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.
Weakness: CWE-345
Which versions are affected by CVE-2026-45057?
3 open source packages ship an affected version, including matrix-sdk-ui.
| Package | Affected | Fixed in |
|---|---|---|
matrix-sdk-ui crates.io | All versions | 0.16.1 |
matrix-sdk-ui crates.io | All versions | 0.16.1 |
matrix-sdk-ui crates.io | From 0.0.0-0 | 0.16.1 |
How do I fix CVE-2026-45057?
Upgrade matrix-sdk-ui to 0.16.1 or later.
Upgrade, and check permissions on every request on the server, not only in the interface. More about Missing authorization.
Is CVE-2026-45057 being exploited?
There is no known exploitation of CVE-2026-45057 in the wild and no public exploit code.
Sources
Also known as GHSA-h97m-27fx-42rx, RUSTSEC-2026-0158.