CVE-2024-13961 is a local privilege escalation vulnerability identified in Avast CleanUp Premium version 24.2.16593.17810 running on Windows 10 Pro x64. The vulnerability arises from improper link resolution before file access in the TuneupSvc service component of the product. Specifically, it involves a Time-of-Check to Time-of-Use (TOCTTOU) race condition that allows a local attacker to create a symbolic link (symlink) to manipulate the file system operations performed by the service. By exploiting this flaw, an attacker with limited privileges can escalate their rights to SYSTEM level, enabling the execution of arbitrary code with the highest privileges on the affected machine. The vulnerability is classified under CWE-59 (Improper Link Resolution Before File Access) and CWE-367 (Time-of-Check Time-of-Use Race Condition). The CVSS v3.1 base score is 7.8, indicating a high severity level, with attack vector being local (AV:L), requiring low attack complexity (AC:L), low privileges (PR:L), no user interaction (UI:N), and impacting confidentiality, integrity, and availability (all rated high). Although no public exploits are currently known in the wild, the nature of the vulnerability makes it a significant risk for local attackers aiming to gain full control over affected systems. The vulnerability specifically targets the TuneupSvc service, which likely runs with elevated privileges, making the exploitation feasible once local access is obtained. This flaw can be leveraged in scenarios where an attacker already has some form of local access, such as through a compromised user account or via other attack vectors that grant limited system access.

For European organizations, the impact of CVE-2024-13961 can be substantial. Since Avast CleanUp Premium is a widely used system optimization and maintenance tool, especially in enterprise and consumer environments, the presence of this vulnerability could allow attackers who have gained local access to escalate privileges to SYSTEM level. This could lead to full system compromise, enabling attackers to install persistent malware, exfiltrate sensitive data, disrupt system operations, or move laterally within the network. The high impact on confidentiality, integrity, and availability means that critical business data and services could be at risk. Organizations relying on Avast CleanUp Premium as part of their endpoint management or maintenance routines may face increased risk of insider threats or post-exploitation attacks. Additionally, because the vulnerability does not require user interaction and has low attack complexity, it could be exploited quickly once local access is achieved, increasing the urgency for mitigation. The lack of known exploits in the wild currently reduces immediate risk but does not eliminate the potential for future exploitation, especially as threat actors often reverse-engineer disclosed vulnerabilities to develop exploits.

To mitigate CVE-2024-13961 effectively, European organizations should take the following specific actions: 1) Immediately update Avast CleanUp Premium to a patched version once available from the vendor, as no patch links are currently provided but should be prioritized upon release. 2) Restrict local access to systems running Avast CleanUp Premium by enforcing strict access controls and limiting user privileges to the minimum necessary, reducing the likelihood of an attacker gaining the initial foothold required for exploitation. 3) Monitor and audit local user activities, especially those involving file system operations and symbolic link creations, to detect potential exploitation attempts. 4) Employ application whitelisting and endpoint detection and response (EDR) solutions to identify and block suspicious behaviors related to privilege escalation and unauthorized code execution. 5) Educate IT and security teams about the TOCTTOU attack vector and the specific risks associated with symbolic link manipulation to improve incident response readiness. 6) Consider temporarily disabling or uninstalling Avast CleanUp Premium on critical systems if patching is delayed and the risk of local compromise is high. 7) Implement robust endpoint hardening practices, including disabling unnecessary services and enforcing secure configurations to reduce the attack surface.