CVE-2017-2221 in IME
Summary
by MITRE
Untrusted search path vulnerability in Installer of Baidu IME Ver3.6.1.6 and earlier allows an attacker to gain privileges via a Trojan horse DLL in an unspecified directory.
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Analysis
by VulDB Data Team • 11/03/2019
The vulnerability identified as CVE-2017-2221 represents a critical untrusted search path weakness within the Baidu IME installer component version 3.6.1.6 and earlier. This flaw resides in the installer's dynamic link library loading mechanism, where the software fails to properly validate or sanitize the search path used to locate required DLL files during the installation process. The vulnerability manifests when the installer processes a Trojan horse DLL file placed in an unspecified directory that is part of the system's search path. This creates a privilege escalation vector that attackers can exploit to execute arbitrary code with elevated privileges, potentially compromising the entire system.
The technical implementation of this vulnerability aligns with CWE-426, which describes untrusted search path vulnerabilities where applications use external search paths without proper validation. The installer component likely employs standard Windows DLL loading behavior, where it searches for required libraries in a predetermined order including the current working directory, system directories, and user-specific paths. When an attacker places a malicious DLL with the same name as a legitimate library in a directory that is searched before the legitimate library location, the system loads the malicious code instead of the intended component. This behavior violates the principle of least privilege and creates a fundamental security flaw in the software's trust model.
From an operational perspective, this vulnerability presents significant risk to end-user systems as it allows for privilege escalation without requiring user interaction beyond the initial installation process. Attackers can leverage this weakness by placing malicious DLL files in directories that the installer will search, effectively hijacking the installation process to execute malicious code with the privileges of the user performing the installation. The impact extends beyond simple code execution, as successful exploitation can lead to full system compromise, persistence mechanisms, data exfiltration, and lateral movement within network environments. The vulnerability's stealth nature makes it particularly dangerous since legitimate installation processes continue to function normally while malicious code executes in the background.
Mitigation strategies for CVE-2017-2221 should focus on both immediate remediation and long-term architectural improvements. The most effective immediate solution involves updating to Baidu IME version 3.6.1.7 or later, where the vendor has implemented proper DLL search path validation and secure loading mechanisms. Organizations should also implement application whitelisting policies that restrict which executables can run on systems, particularly in high-risk environments. Network segmentation and privilege separation can help limit the potential impact of successful exploitation. Additionally, system administrators should conduct regular security audits to identify and remove unauthorized DLL files from system directories. The vulnerability's classification under ATT&CK technique T1059.001 for command and scripting interpreter and T1068 for exploit for privilege escalation highlights the need for comprehensive endpoint protection measures including behavioral monitoring and file integrity checks. Organizations should also consider implementing least privilege principles for installation processes and regularly review system search paths to eliminate potentially dangerous directory entries.