CVE-2024-50336 identifies a path traversal vulnerability in the matrix-js-sdk, a JavaScript client-server SDK implementing the Matrix messaging protocol. The flaw exists in versions before 34.11.1 and is caused by improper validation and limitation of pathname inputs when processing MXC URIs. MXC URIs are used within the Matrix ecosystem to reference media content. A malicious actor who is a member of a Matrix room can craft specially designed MXC URIs that exploit this vulnerability, causing the client to perform arbitrary authenticated GET requests against the victim's homeserver. This behavior effectively allows the attacker to access restricted resources or data that the client is authorized to access, bypassing intended access controls on the client side. The vulnerability does not require user interaction and can be triggered remotely by a low-privileged attacker (room member) without authentication elevation. The CVSS 4.0 base score is 5.3 (medium), reflecting network attack vector, low attack complexity, no privileges required, no user interaction, and limited impact on integrity and availability but some impact on confidentiality. The flaw was addressed in matrix-js-sdk version 34.11.1 by properly restricting pathname traversal in MXC URI handling, preventing unauthorized requests. No public exploits or widespread attacks have been reported to date.

For European organizations, this vulnerability poses a risk of unauthorized data exposure and potential leakage of sensitive information stored or accessible via the Matrix homeserver. Since the attack can be initiated by any malicious room member, insider threats or compromised accounts could exploit this to access confidential data or internal endpoints. This could undermine the confidentiality and integrity of communications, especially in sectors relying on Matrix for secure messaging such as government, finance, and healthcare. The vulnerability could also be leveraged for reconnaissance or lateral movement within an organization's network if the homeserver hosts internal APIs or sensitive resources. Although the impact on availability is limited, the breach of confidentiality and trust in secure communications can have significant reputational and compliance consequences under regulations like GDPR. Organizations using matrix-js-sdk-based clients should consider this vulnerability a moderate risk and act promptly to update and audit their Matrix deployments.

The primary mitigation is to upgrade all matrix-js-sdk clients to version 34.11.1 or later, where the vulnerability is fixed. Organizations should enforce strict version control and patch management policies for all Matrix clients and servers. Additionally, review and restrict room membership to trusted users only, minimizing exposure to malicious actors. Implement monitoring and anomaly detection on homeserver logs to identify unusual authenticated GET requests that could indicate exploitation attempts. Harden homeserver configurations to limit access to sensitive internal endpoints and apply strict access controls on resources accessible via the client. Consider deploying Web Application Firewalls (WAFs) or API gateways that can detect and block suspicious path traversal patterns in requests. Finally, educate users and administrators about the risks of malicious room members and encourage reporting of suspicious activity.