CVE-2016-7222 in Windows
Summary
by MITRE
Task Scheduler in Microsoft Windows 10 Gold, 1511, and 1607 and Windows Server 2016 allows local users to gain privileges via a crafted UNC pathname in a task, aka "Task Scheduler Elevation of Privilege Vulnerability."
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Analysis
by VulDB Data Team • 09/29/2022
The CVE-2016-7222 vulnerability represents a critical elevation of privilege flaw within Microsoft Windows Task Scheduler components affecting multiple Windows versions including Windows 10 Gold, 1511, 1607, and Windows Server 2016. This vulnerability operates through a specific manipulation of UNC (Universal Naming Convention) pathnames within scheduled tasks, creating a privilege escalation vector that allows local attackers to execute malicious code with elevated privileges. The flaw stems from improper validation of UNC pathnames when processing scheduled tasks, specifically when the Task Scheduler attempts to resolve network paths without adequate security checks. This vulnerability falls under the CWE-787 weakness category, which describes out-of-bounds write conditions, though the primary exploitation mechanism involves improper input validation and privilege handling. The vulnerability enables attackers to leverage the Task Scheduler's legitimate functionality to gain system-level privileges, fundamentally undermining the security model of the operating system.
The technical exploitation mechanism involves crafting a malicious UNC pathname within a scheduled task that points to a network resource controlled by the attacker. When the Task Scheduler processes this task, it attempts to resolve the UNC path without sufficient validation, potentially causing the system to execute code from the attacker-controlled location with elevated privileges. This occurs because the Task Scheduler service runs with high privileges and processes UNC paths without proper sandboxing or access control verification. The vulnerability specifically affects the way Windows handles UNC paths in scheduled tasks, where the system fails to properly validate the network resource before attempting to access it. This flaw aligns with ATT&CK technique T1053 which covers scheduled task/job manipulation, and T1068 which covers local privilege escalation through system-level access. The exploitation requires local access to the system but does not require network connectivity to external resources, making it particularly dangerous as it can be leveraged by any local user to escalate their privileges to SYSTEM level access.
The operational impact of CVE-2016-7222 is severe and far-reaching across enterprise environments, as it provides a straightforward path for local attackers to gain system-level privileges without requiring additional attack vectors or complex exploitation techniques. Once exploited, the vulnerability allows attackers to execute arbitrary code with full system privileges, potentially enabling complete system compromise, data exfiltration, or establishment of persistent backdoors. The vulnerability affects all supported versions of Windows 10 and Windows Server 2016, making it particularly concerning for organizations that have not yet migrated to newer operating systems. Organizations running these affected versions face increased risk of lateral movement within their networks, as attackers can use the elevated privileges to access other systems and resources. The vulnerability also impacts security monitoring and incident response capabilities, as the exploitation may not generate obvious indicators of compromise in traditional security logs. This is because the legitimate Task Scheduler functionality is being abused rather than a direct system call or API manipulation, making detection more challenging.
Mitigation strategies for CVE-2016-7222 should include immediate deployment of Microsoft security updates and patches that address the vulnerability in the Task Scheduler component. Organizations should implement strict access controls and permissions for scheduled tasks, particularly avoiding the use of UNC paths in tasks that run with elevated privileges. Network administrators should consider implementing network segmentation and access control measures to limit potential exploitation pathways. Security teams should monitor for suspicious scheduled task creation or modification activities and establish baseline configurations for Task Scheduler that restrict UNC path usage. The vulnerability highlights the importance of principle of least privilege implementation and proper input validation in system components. Additionally, organizations should consider implementing endpoint detection and response solutions that can identify anomalous Task Scheduler behavior or suspicious UNC path resolution attempts. Regular security assessments should verify that scheduled tasks do not utilize potentially dangerous UNC path configurations, and system administrators should be trained to recognize and properly configure scheduled tasks to avoid exploitation vectors. The vulnerability serves as a reminder of the critical importance of validating all input sources, particularly in system-level components that operate with elevated privileges, and demonstrates the need for comprehensive security controls beyond traditional perimeter defenses.