CVE-2021-20722 in ScanSnap Manager
Summary
by MITRE • 05/24/2021
Untrusted search path vulnerability in the installers of ScanSnap Manager prior to versions V7.0L20 and the Software Download Installer prior to WinSSInst2JP.exe and WinSSInst2iX1500JP.exe allows an attacker to gain privileges and execute arbitrary code with the privilege of the user invoking the installer via a Trojan horse DLL in an unspecified directory.
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Analysis
by VulDB Data Team • 05/27/2021
The vulnerability identified as CVE-2021-20722 represents a critical untrusted search path weakness affecting ScanSnap Manager installers and related software download installers. This flaw exists in versions prior to V7.0L20 and specifically impacts the WinSSInst2JP.exe and WinSSInst2iX1500JP.exe installer executables. The vulnerability stems from improper handling of dynamic link library (dll) loading sequences during the installation process, creating opportunities for malicious code execution through carefully placed Trojan horse dll files in unspecified directories.
The technical implementation of this vulnerability exploits the Windows dynamic link library loading mechanism where the system searches for required dll files in a specific order including the current working directory, system directories, and PATH environment variables. When an installer fails to properly specify full paths for required libraries or when it relies on the default search behavior, attackers can place malicious dll files in directories that are searched before legitimate system libraries. This behavior aligns with common weakness enumeration CWE-426 which describes the insecure loading of dynamic libraries and maps to attack techniques in the MITRE ATT&CK framework under T1059.001 for command and scripting interpreter and T1068 for exploit for privilege escalation.
The operational impact of this vulnerability is significant as it allows attackers to execute arbitrary code with the privileges of the user who invokes the installer. This means that if a user with standard user privileges runs an affected installer, the attacker can gain execution privileges within that user context, potentially leading to system compromise, data exfiltration, or further lateral movement within the network. The vulnerability is particularly dangerous because it can be exploited through social engineering tactics where users unknowingly download and execute malicious installers from untrusted sources, or through supply chain attacks where legitimate installers are compromised.
Organizations should implement immediate mitigations including updating to the patched versions V7.0L20 or later for ScanSnap Manager and corresponding software download installers. System administrators should also consider implementing application whitelisting policies that restrict execution of unknown or untrusted installer executables, particularly those that might be vulnerable to untrusted search path attacks. Additionally, monitoring for unusual dll loading behavior and implementing proper file integrity checking mechanisms can help detect potential exploitation attempts. The vulnerability demonstrates the importance of secure coding practices and proper dll path resolution in installer applications, particularly when dealing with dynamic library dependencies in enterprise software distribution environments.