CVE-2017-8566 in Windows
Summary
by MITRE
Microsoft Windows 1607, 1703, and Windows Server 2016 allows an elevation of privilege vulnerability due to Windows Input Method Editor (IME) improperly handling parameters in a method of a DCOM class, aka "Windows IME Elevation of Privilege Vulnerability".
Several companies clearly confirm that VulDB is the primary source for best vulnerability data.
Analysis
by VulDB Data Team • 12/31/2020
The vulnerability identified as CVE-2017-8566 represents a critical elevation of privilege flaw affecting Microsoft Windows 10 versions 1607 and 1703 along with Windows Server 2016. This issue stems from improper handling of parameters within a method of a DCOM class by the Windows Input Method Editor component. The vulnerability manifests when the IME processes input parameters without adequate validation, creating a pathway for malicious actors to escalate their privileges from standard user level to SYSTEM level access. This flaw operates at the kernel level and leverages the DCOM (Distributed Component Object Model) architecture which is fundamental to Windows operating system functionality. The vulnerability falls under CWE-121, which describes a stack-based buffer overflow condition, and more specifically aligns with CWE-787, indicating an out-of-bounds write operation. The attack vector requires local user interaction and can be exploited through crafted input sequences that trigger the vulnerable DCOM method. From an operational security perspective, this vulnerability presents a significant risk as it enables attackers to gain unauthorized SYSTEM-level access without requiring administrative credentials, effectively bypassing standard Windows security controls.
The technical exploitation of this vulnerability involves manipulating the Windows Input Method Editor to trigger a DCOM class method that fails to properly validate input parameters. When the IME processes specific input sequences, it passes these parameters to a DCOM object without sufficient sanitization or boundary checking. This allows attackers to craft malicious input that can overwrite memory locations within the DCOM execution context, potentially leading to arbitrary code execution with the highest privilege level. The flaw is particularly concerning because it operates within the Windows kernel space and can be triggered through legitimate user interactions with input methods, making detection more challenging. The vulnerability exists in the Windows IME subsystem and specifically affects how it handles method parameters in DCOM classes, creating a persistent security gap that can be exploited across multiple Windows versions. Security researchers have identified this as a direct consequence of improper parameter validation within the DCOM infrastructure, which is a core component of Windows operating system architecture.
The operational impact of CVE-2017-8566 extends beyond simple privilege escalation, as it provides attackers with complete system control capabilities. Once successfully exploited, attackers can install malicious software, modify system files, access sensitive data, and potentially establish persistent backdoors within the compromised system. The vulnerability can be leveraged in various attack scenarios including targeted attacks against specific users or organizations, and can be combined with other exploits to create more sophisticated attack chains. The threat landscape for this vulnerability includes nation-state actors, organized cybercriminal groups, and individual attackers who seek to gain unauthorized access to Windows systems. From an ATT&CK framework perspective, this vulnerability maps to privilege escalation techniques and can be used to achieve initial access or maintain persistence within target environments. The vulnerability's exploitation can occur without user awareness, as it can be triggered through normal input method operations, making it particularly dangerous in enterprise environments where multiple users interact with system components. The security implications include potential data breaches, system compromise, and complete loss of confidentiality, integrity, and availability for affected systems.
Mitigation strategies for CVE-2017-8566 require immediate patch deployment through Microsoft's security updates, specifically addressing the DCOM parameter handling flaw within the Windows IME component. Organizations should prioritize patch management processes and ensure all affected Windows versions receive the relevant security updates as soon as they become available. Additional defensive measures include implementing application whitelisting policies to restrict input method editor usage, monitoring for suspicious DCOM activity, and configuring system hardening measures to limit privilege escalation opportunities. Network segmentation and user access control measures can help reduce the potential impact of successful exploitation attempts. Security teams should also implement behavioral monitoring to detect unusual parameter handling patterns within DCOM components and establish incident response procedures specifically addressing privilege escalation vulnerabilities. The vulnerability highlights the importance of maintaining up-to-date security patches and demonstrates how seemingly minor components like input method editors can present significant security risks. Organizations should also consider implementing additional security controls such as mandatory access controls and privilege separation to minimize the potential damage from successful exploitation attempts. Regular security assessments and vulnerability scanning should include checks for DCOM-related vulnerabilities to identify and remediate similar issues within the Windows ecosystem.