CVE-2017-12410 in Virtual System Administrator
Summary
by MITRE
It is possible to exploit a Time of Check & Time of Use (TOCTOU) vulnerability by winning a race condition when Kaseya Virtual System Administrator agent 9.3.0.11 and earlier tries to execute its binaries from working and/or temporary folders. Successful exploitation results in the execution of arbitrary programs with "NT AUTHORITY\SYSTEM" privileges.
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Analysis
by VulDB Data Team • 01/16/2020
The vulnerability identified as CVE-2017-12410 represents a critical time-of-check to time-of-use (TOCTOU) flaw within the Kaseya Virtual System Administrator agent version 9.3.0.11 and earlier. This type of vulnerability occurs when a system performs a security check on a resource and then subsequently uses that same resource before another process can alter it, creating a window of opportunity for malicious exploitation. The affected Kaseya agent operates with elevated privileges and attempts to execute binaries from working and temporary directories, making it particularly susceptible to this class of attack. The vulnerability stems from inadequate synchronization mechanisms during the binary execution process, where the system checks file permissions and then proceeds to execute the binary without revalidating the resource integrity between the check and use phases.
The technical implementation of this vulnerability involves a race condition scenario where an attacker can manipulate temporary or working directories to replace legitimate executable files with malicious ones. When the Kaseya agent performs its operations, it first validates the existence and permissions of binaries in temporary directories before executing them. During this brief window between validation and execution, an attacker can substitute the legitimate binary with a malicious payload that will be executed with the highest privileges available to the agent. This privilege escalation occurs because the Kaseya agent runs with "NT AUTHORITY\SYSTEM" privileges, which provides complete control over the target system. The flaw is particularly dangerous because it leverages the agent's legitimate behavior of working with temporary files, making the attack vector both subtle and effective.
The operational impact of this vulnerability extends beyond simple privilege escalation to encompass complete system compromise. Successful exploitation allows attackers to execute arbitrary code with system-level privileges, enabling them to install backdoors, exfiltrate data, modify system configurations, or establish persistent access to the compromised environment. The attack surface is particularly concerning for organizations using Kaseya VSA agents, as these systems often manage critical infrastructure components and may have access to sensitive data. The vulnerability's exploitation does not require special privileges beyond basic user access to the system, making it accessible to a wide range of threat actors. Organizations that rely on Kaseya for system management and monitoring face significant risk, as the compromised agent could provide attackers with a foothold to move laterally across the network and target other systems within the organization's infrastructure.
Mitigation strategies for CVE-2017-12410 must address both immediate remediation and long-term security hardening measures. The most direct solution involves upgrading to Kaseya VSA version 9.3.0.12 or later, which contains patches specifically designed to eliminate the race condition vulnerability. Organizations should also implement directory permission controls to prevent unauthorized modification of temporary and working directories used by the agent, ensuring that only authorized processes can modify these locations. The principle of least privilege should be enforced by running the agent with minimal required permissions rather than system-level privileges whenever possible. Additionally, organizations should implement monitoring solutions that can detect anomalous file system activities in temporary directories and establish regular security audits to identify potential manipulation attempts. From a defensive perspective, this vulnerability aligns with ATT&CK technique T1059.001 for command and scripting interpreter and T1068 for exploit for privilege escalation, making it a significant concern for security teams implementing threat hunting and incident response procedures. The vulnerability also relates to CWE-367 which specifically addresses time-of-check to time-of-use flaws, emphasizing the need for proper synchronization mechanisms in security-critical code paths.