What is CVE-2026-45057?

CVE-2026-45057 is a medium-severity vulnerability in Matrix-Org Matrix-Sdk-Ui, classified under Insufficient Verification of Data Authenticity. CVSS score: 4.9/10. Published 2026-09-11.

How severe is CVE-2026-45057?

Medium severity. CVSS v3 base score is 4.9 out of 10.

Vulnerability in Matrix-Org Matrix-Sdk-Ui

CVE-2026-45057

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.

CVSS v3 metric

CVSS v3 base score 4.9 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:H/A:N.

Affected products

Matrix-org Matrix-sdk-ui — versions < 0.16.1

Weakness classification (CWE)

CWE-345 — Insufficient Verification of Data Authenticity

References

security-advisories@github.com (x_refsource_MISC)
security-advisories@github.com (x_refsource_MISC)
security-advisories@github.com (x_refsource_CONFIRM)
security-advisories@github.com (x_refsource_MISC)

Frequently asked questions

What is CVE-2026-45057?: CVE-2026-45057 is a medium-severity vulnerability in Matrix-Org Matrix-Sdk-Ui, classified under Insufficient Verification of Data Authenticity. CVSS score: 4.9/10. Published 2026-09-11.
How severe is CVE-2026-45057?: Medium severity. CVSS v3 base score is 4.9 out of 10.