PYSEC-2026-842

Dashboard / Vulnerabilities / PYSEC-2026-842

PYSEC-2026-842

Summary: When matrix-nio receives forwarded room keys, the receiver doesn't check if it requested the key from the forwarder

Details: When matrix-nio before 0.20 requests a room key from our devices, it correctly accepts key forwards only if they are a response to a previous request. However, it doesn't check that the device that responded matches the device the key was requested from. This allows a malicious homeserver to insert room keys of questionable validity into the key store in some situations, potentially assisting in an impersonation attack. ### For more information If you have any questions or comments about this advisory, e-mail us at [[email protected]](mailto:[email protected]).

References: https://github.com/poljar/matrix-nio/security/advisories/GHSA-w4pr-4vjg-hffh, https://nvd.nist.gov/vuln/detail/CVE-2022-39254, https://github.com/poljar/matrix-nio/commit/b1cbf234a831daa160673defd596e6450e9c29f0, https://github.com/poljar/matrix-nio, https://pypi.org/project/matrix-nio, https://github.com/advisories/GHSA-w4pr-4vjg-hffh