CVE-2022-24883 is a medium-severity vulnerability affecting FreeRDP server implementations prior to version 2.7.0. FreeRDP is an open-source implementation of the Remote Desktop Protocol (RDP), widely used for remote access to Windows and other systems. The vulnerability arises from improper authentication (CWE-287) when the server is configured to authenticate users against a Security Account Manager (SAM) file. Specifically, if the server is configured with an invalid SAM file path, the authentication mechanism may erroneously succeed even when invalid credentials are provided. This flaw is due to the server-side logic failing to properly verify the presence and validity of the SAM file before authenticating users. Notably, FreeRDP-based clients are not affected by this issue; only server implementations that rely on FreeRDP for SAM file authentication are vulnerable. The vulnerability was addressed in FreeRDP version 2.7.0, which includes fixes to ensure proper validation of the SAM file path and authentication process. As an interim mitigation, administrators can implement custom authentication callbacks via the HashCallback mechanism or ensure that the SAM database path is correctly configured and accessible with valid file handles. There are no known exploits in the wild targeting this vulnerability as of the published date, and no CVSS score has been assigned. The vulnerability's root cause is improper authentication logic, which can lead to unauthorized access if exploited, potentially allowing attackers to bypass credential checks on affected RDP servers.

For European organizations, the impact of this vulnerability could be significant, particularly for those relying on FreeRDP server implementations for remote desktop services that authenticate against SAM files. Successful exploitation could allow unauthorized users to gain remote access without valid credentials, compromising confidentiality and integrity of sensitive data and systems. This could lead to lateral movement within networks, data exfiltration, or deployment of further malicious payloads. Availability could also be indirectly affected if attackers disrupt services or deploy ransomware. Organizations in sectors with high reliance on remote access, such as finance, healthcare, government, and critical infrastructure, are at greater risk. Given that FreeRDP is often used in mixed OS environments and by organizations seeking open-source RDP solutions, the vulnerability could expose a broad range of systems. However, the requirement for server-side misconfiguration (invalid SAM file path) somewhat limits the scope, as properly configured servers are not vulnerable. Still, misconfigurations are common in complex environments, increasing the risk. The absence of known exploits reduces immediate threat but does not eliminate risk, especially as attackers may develop exploits over time.

1. Upgrade all FreeRDP server implementations to version 2.7.0 or later to apply the official fix addressing the improper authentication issue. 2. Audit and verify the SAM file path configuration on all FreeRDP-based RDP servers to ensure paths are valid, accessible, and that the application maintains necessary file handles. 3. Implement custom authentication mechanisms using the HashCallback feature to enforce stricter credential validation and reduce reliance on SAM file authentication. 4. Conduct regular configuration reviews and automated checks to detect invalid or missing SAM file paths and other misconfigurations that could lead to authentication bypass. 5. Monitor RDP server logs for unusual authentication successes or failures that could indicate exploitation attempts. 6. Restrict network access to RDP servers using firewall rules, VPNs, or zero-trust network access solutions to limit exposure to potential attackers. 7. Educate system administrators on the importance of correct SAM file configuration and the risks of improper authentication setups. 8. Employ endpoint detection and response (EDR) tools to detect anomalous remote access behaviors that might indicate exploitation attempts.