The security threat concerns a privilege escalation vulnerability in RDPGuard version 9.9.9, a Windows-based software designed to protect Remote Desktop Protocol (RDP) services from brute-force attacks by blocking suspicious IP addresses. The exploit leverages a feature within RDPGuard that allows users to configure custom actions triggered by specific events, such as an IP block. Specifically, an attacker can create a malicious batch (.bat) file containing reverse shell commands and configure RDPGuard to execute this file when an IP block event occurs. By triggering the "Test Run" function within the Custom Actions/Notifications interface, the attacker can execute the batch file with SYSTEM-level privileges, effectively gaining NT AUTHORITY\SYSTEM access on the host machine. This escalation bypasses normal privilege boundaries, granting full control over the system. The exploit was demonstrated on Windows 10 (32-bit) and requires local access to the RDPGuard interface to configure the malicious action. The exploit code is presented as a textual description of steps rather than a traditional script, indicating the attack vector is through misuse of legitimate software functionality rather than a direct code injection or memory corruption vulnerability. No patches or vendor mitigations are currently linked, and there are no known exploits in the wild at the time of reporting. The vulnerability is classified as a local exploit, meaning that initial access to the system or software interface is necessary to carry out the attack.

For European organizations, this vulnerability poses a significant risk, especially for those relying on RDPGuard to secure their RDP endpoints. Successful exploitation results in full SYSTEM-level access, which can lead to complete compromise of affected systems. Attackers could deploy malware, exfiltrate sensitive data, disable security controls, or move laterally within the network. Given that RDPGuard is used to protect RDP services—a common attack vector—this vulnerability ironically undermines the security posture of organizations relying on it. The impact is particularly severe for critical infrastructure, financial institutions, healthcare providers, and government agencies where RDP access is prevalent and system integrity is paramount. The requirement for local access limits remote exploitation but insider threats or attackers who have already gained foothold via other means could leverage this vulnerability to escalate privileges rapidly. Additionally, the lack of patches or vendor guidance increases the window of exposure. Organizations with automated incident response or monitoring might detect unusual execution of batch files or reverse shells, but without proactive mitigation, the risk remains high.

1. Restrict access to the RDPGuard management interface strictly to trusted administrators using network segmentation and multi-factor authentication to prevent unauthorized local configuration changes. 2. Monitor and audit the Custom Actions/Notifications settings within RDPGuard regularly to detect unauthorized additions or modifications, especially any that execute external scripts or programs. 3. Implement application whitelisting or endpoint protection solutions that prevent execution of unauthorized batch files or reverse shells, particularly those launched by RDPGuard processes. 4. Employ strict file system permissions to limit who can create or modify batch files in directories accessible by RDPGuard. 5. If possible, disable or limit the use of the Custom Actions feature within RDPGuard until a vendor patch or official mitigation is available. 6. Maintain comprehensive logging of RDPGuard events and integrate with SIEM solutions to detect anomalous activity such as unexpected program executions triggered by IP block events. 7. Engage with the vendor to obtain updates or patches addressing this vulnerability and apply them promptly once available. 8. Conduct internal penetration testing and red team exercises to validate that privilege escalation paths via RDPGuard are mitigated.