CVE-2023-34046 in Fusion
Summary
by MITRE • 10/25/2023
VMware Fusion(13.x prior to 13.5) contains a TOCTOU (Time-of-check Time-of-use) vulnerability that occurs during installation for the first time (the user needs to drag or copy the application to a folder from the '.dmg' volume) or when installing an upgrade. A malicious actor with local non-administrative user privileges may exploit this vulnerability to escalate privileges to root on the system where Fusion is installed or being installed for the first time.
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Analysis
by VulDB Data Team • 11/12/2023
The vulnerability identified as CVE-2023-34046 represents a critical time-of-check time-of-use flaw within VMware Fusion versions 13.x prior to 13.5. This security weakness manifests specifically during the initial installation process or when upgrading existing installations, creating a window of opportunity for privilege escalation attacks. The vulnerability stems from improper handling of file operations where the system performs a check for file permissions or existence at one point in time, only to use different file references or locations at a subsequent point. This temporal discrepancy allows malicious actors to manipulate the system state between the check and use phases, effectively bypassing intended security controls. The flaw particularly affects the installation process where users must drag or copy the application from a .dmg volume to a target folder, creating a scenario where the system's validation logic can be exploited through carefully timed file system modifications.
The technical implementation of this TOCTOU vulnerability involves the application's installation mechanism failing to maintain consistent state validation throughout the copy operation process. When VMware Fusion performs its initial setup or upgrade procedure, the system checks certain conditions such as file permissions, directory existence, or security attributes before proceeding with the actual installation steps. However, the time gap between this validation and the actual file operations allows a local attacker to modify the target locations, replace files, or manipulate symbolic links in ways that would not be detected by the initial check. This particular weakness aligns with CWE-367, which specifically addresses time-of-check to time-of-use flaws, and demonstrates how improper synchronization of system state validation can create persistent security vulnerabilities. The vulnerability is particularly concerning because it operates entirely within the installation context where legitimate administrative privileges are required, making it an attractive target for attackers seeking to gain elevated system access.
The operational impact of this vulnerability extends beyond simple privilege escalation to encompass potential system compromise and persistent access capabilities. A local non-administrative user who successfully exploits this vulnerability can achieve root-level privileges, effectively bypassing all standard user access controls and system security measures. This escalation allows the attacker to modify system files, install malicious software, access sensitive data, and potentially establish backdoors for continued access. The vulnerability is particularly dangerous because it affects the installation process itself, meaning that any user with the ability to initiate a Fusion installation or upgrade can potentially exploit this flaw. The attack vector is relatively straightforward requiring only local system access and knowledge of the specific installation timing window. This vulnerability represents a significant risk to organizations where users might have access to systems running affected VMware Fusion versions, as it can be exploited without requiring network connectivity or specialized attack infrastructure.
Mitigation strategies for CVE-2023-34046 focus on both immediate remediation and long-term architectural improvements. The primary and most effective solution involves upgrading to VMware Fusion version 13.5 or later, where the TOCTOU vulnerability has been addressed through proper state validation mechanisms. Organizations should implement immediate patch management protocols to ensure all affected systems receive updates as soon as possible. Additionally, system administrators should consider implementing additional security controls such as restricting user access to installation processes, monitoring for unusual file system modifications during installation, and employing application whitelisting solutions to prevent unauthorized software installation. From an ATT&CK framework perspective, this vulnerability maps to techniques involving privilege escalation through software exploitation and credential access through local system manipulation. The vulnerability also highlights the importance of secure coding practices and proper state validation in installation processes, emphasizing the need for developers to implement robust synchronization mechanisms that prevent temporal gaps in security checks. Organizations should also consider implementing monitoring solutions that can detect anomalous installation behavior or file system modifications that might indicate exploitation attempts.