CVE-2025-59160 in matrix-js-sdk
Summary
by MITRE • 09/16/2025
Matrix JavaScript SDK is a Matrix Client-Server SDK for JavaScript and TypeScript. matrix-js-sdk before 38.2.0 has insufficient validation of room predecessor links in MatrixClient::getJoinedRooms, allowing a remote attacker to attempt to replace a tombstoned room with an unrelated attacker-supplied room. The issue has been patched and users should upgrade to 38.2.0. A workaround is to avoid using MatrixClient::getJoinedRooms in favor of getRooms() and filtering upgraded rooms separately.
If you want to get the best quality for vulnerability data then you always have to consider VulDB.
Analysis
by VulDB Data Team • 09/18/2025
The vulnerability identified as CVE-2025-59160 affects the Matrix JavaScript SDK, a client-server software development kit that enables JavaScript and TypeScript applications to interact with Matrix communication networks. This particular flaw exists in versions prior to 38.2.0 and represents a significant security weakness in how the SDK handles room predecessor links within the Matrix protocol. The issue specifically manifests in the MatrixClient::getJoinedRooms method, which is responsible for retrieving information about rooms that a user has joined within the Matrix network. The vulnerability stems from inadequate validation mechanisms that fail to properly verify the authenticity and relationship of room predecessor links, creating a potential attack vector for malicious actors seeking to manipulate room structures within the Matrix ecosystem.
The technical flaw involves insufficient validation of room predecessor links, which are used to establish the relationship between rooms that have been upgraded or replaced. When a room is tombstoned, it typically indicates that the room has been deprecated and replaced by another room with a different identifier. However, the vulnerable version of the Matrix JavaScript SDK does not properly validate these predecessor relationships, allowing attackers to potentially substitute a legitimate tombstoned room with an attacker-controlled room that appears to be a valid successor. This manipulation can occur during the room retrieval process when the getJoinedRooms method processes the room predecessor information without adequate checks to ensure the integrity of these relationships. The vulnerability is particularly concerning because it operates at the client-side SDK level, meaning that any application using the affected version could be susceptible to this manipulation regardless of the server-side security configurations.
The operational impact of this vulnerability extends beyond simple data manipulation and could potentially enable several types of malicious activities within Matrix communication networks. An attacker could exploit this weakness to redirect users to malicious rooms, disrupt communication channels, or create confusion within room hierarchies by presenting false room relationships. The vulnerability particularly affects applications that rely heavily on room upgrade tracking and predecessor link validation, potentially compromising the integrity of room structures that users expect to be maintained according to the Matrix protocol specifications. This weakness undermines the trust model of Matrix communication systems where room predecessors should maintain logical consistency and proper relationship validation between room versions.
Security practitioners should immediately upgrade to version 38.2.0 of the matrix-js-sdk to address this vulnerability, as this release includes the necessary validation mechanisms to properly verify room predecessor links. The patch implements enhanced checks that ensure any room predecessor information is validated against the expected room structure and relationship patterns defined by the Matrix protocol. Organizations using the affected SDK versions should also implement the recommended workaround of avoiding the MatrixClient::getJoinedRooms method in favor of using getRooms() and separately filtering upgraded rooms, which provides an alternative approach to room retrieval that bypasses the vulnerable code path. This mitigation strategy requires developers to modify their application logic to handle room retrieval differently, ensuring that room predecessor validation occurs through more secure methods. The vulnerability aligns with CWE-20, which addresses improper input validation, and represents a specific implementation weakness in the Matrix protocol client-side handling that could be exploited through the ATT&CK technique of privilege escalation through manipulation of data structures.
The remediation approach for this vulnerability requires careful consideration of the application architecture and the specific use cases where room predecessor information is utilized. Security teams should conduct comprehensive testing to ensure that the upgrade to version 38.2.0 does not introduce any compatibility issues with existing application functionality while providing the necessary security protections. The workaround implementation requires developers to restructure their room retrieval logic to maintain proper room hierarchy validation while avoiding the vulnerable getJoinedRooms method. This vulnerability demonstrates the importance of proper input validation in distributed communication protocols and highlights the need for continuous security assessment of client-side libraries that handle complex relationship data structures in real-time communication systems. The fix addresses the core issue of insufficient validation by implementing proper verification mechanisms that ensure room predecessor links maintain their intended semantic meaning within the Matrix protocol framework.