CVE-2016-7221 in Windows
Summary
by MITRE
Input Method Editor (IME) in Microsoft Windows Vista SP2, Windows Server 2008 SP2 and R2 SP1, Windows 7 SP1, Windows 8.1, Windows Server 2012 Gold and R2, Windows RT 8.1, Windows 10 Gold, 1511, and 1607, and Windows Server 2016 mishandles DLL loading, which allows local users to gain privileges via unspecified vectors, aka "Windows IME Elevation of Privilege Vulnerability."
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Analysis
by VulDB Data Team • 09/29/2022
The Windows Input Method Editor vulnerability identified as CVE-2016-7221 represents a critical privilege escalation flaw affecting multiple versions of the microsoft windows operating system. This vulnerability specifically targets the IME component responsible for handling input methods and text processing, particularly in languages requiring complex character input such as chinese, japanese, and korean. The issue stems from improper handling of dynamic link library loading processes within the IME subsystem, creating opportunities for malicious actors to elevate their privileges from standard user level to system level access. The vulnerability affects a broad range of windows versions including vista sp2, server 2008 sp2 and r2 sp1, windows 7 sp1, windows 8.1, server 2012 gold and r2, windows rt 8.1, windows 10 gold, 1511, and 1607, as well as windows server 2016, demonstrating the widespread nature of this flaw across the microsoft windows ecosystem.
The technical exploitation of this vulnerability occurs through improper dll loading mechanisms within the IME subsystem, where the system fails to properly validate or restrict the loading of dynamic libraries from untrusted locations. This flaw allows local attackers to manipulate the loading sequence of dll files, potentially causing the system to load malicious code with elevated privileges. The vulnerability is classified as a privilege escalation issue under the common weakness enumeration framework as cwe-427, which deals with uncontrolled search path evaluation, and more specifically relates to cwe-78, which addresses command injection vulnerabilities in the context of improper dll loading. The attack vector typically involves a local user executing a crafted payload that leverages the vulnerable IME component to gain elevated privileges, often through the manipulation of system paths or by placing malicious dll files in locations where the IME subsystem will load them automatically.
The operational impact of this vulnerability extends beyond simple privilege escalation, as it provides attackers with complete system control once successfully exploited. An attacker with standard user privileges can leverage this vulnerability to execute arbitrary code with system-level privileges, effectively bypassing the operating system's security model. This capability enables attackers to install malware, modify system files, access sensitive data, and potentially establish persistent access to affected systems. The vulnerability's presence in multiple windows versions means that organizations running any of the affected operating systems are at risk, particularly in enterprise environments where multiple windows versions may be in use simultaneously. The attack surface is further expanded because the IME functionality is typically enabled by default on systems that require complex text input, making exploitation more likely in environments where users regularly utilize these input methods.
Mitigation strategies for CVE-2016-7221 should include immediate application of microsoft security updates and patches released in response to this vulnerability, which address the improper dll loading behavior in the IME subsystem. organizations should implement the principle of least privilege by restricting user access to system resources and avoiding the use of administrator accounts for routine operations. security configurations should include monitoring for suspicious dll loading activities and implementing application whitelisting policies to prevent unauthorized code execution. the mitigation approach aligns with mitre att&ck framework techniques such as t1068, which covers exploit for privilege escalation, and t1059, which addresses command and scripting interpreter. additional defensive measures include regular security audits of system configurations, monitoring for anomalous behavior in the IME subsystem, and ensuring that all windows systems are kept up to date with the latest security patches. administrators should also consider implementing enhanced logging and monitoring specifically for dll loading activities in system processes, as this can help detect potential exploitation attempts before they succeed in elevating privileges.