CVE-2025-66622: Matrix Matrix-Rust-SDK

High severity, CVSS 7.5. EPSS: 0.4% chance of exploitation in the next 30 days.

matrix-sdk-base is the base component to build a Matrix client library. Versions 0.14.1 and prior are unable to handle responses that include custom m.room.join_rules values due to a serialization bug. This can be exploited to cause a denial-of-service condition, if a user is invited to a room with non-standard join rules, the crate's sync process will stall, preventing further processing for all rooms. This is fixed in version 0.16.0.

Affected products

• Matrix Matrix-Rust-SDK: before 0.16.0 (fixed in 0.16.0)

Published 2025-12-09. Last modified 2026-10-07.