CVE-2017-2157 in Public Certification Service for Individuals
Summary
by MITRE
Untrusted search path vulnerability in installers for The Public Certification Service for Individuals "The JPKI user's software (for Windows 7 and later)" Ver3.1 and earlier, The Public Certification Service for Individuals "The JPKI user's software (for Windows Vista)", The Public Certification Service for Individuals "The JPKI user's software" Ver2.6 and earlier that were available until April 27, 2017 allows remote attackers to gain privileges via a Trojan horse DLL in an unspecified directory.
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Analysis
by VulDB Data Team • 09/26/2020
This vulnerability resides in the installer components of Japan's Public Certification Service for Individuals JPKI user software, specifically affecting versions 3.1 and earlier for Windows 7 and later, along with older versions for Windows Vista. The issue manifests as an untrusted search path vulnerability that occurs during the installation process when the software fails to properly validate or sanitize the directories from which it loads dynamic link library files. This flaw creates a dangerous condition where malicious actors can place a specially crafted Trojan horse DLL in an unspecified directory that the installer will subsequently load and execute with elevated privileges. The vulnerability represents a classic path traversal and privilege escalation risk that aligns with CWE-426, which describes the insecure use of system search paths. Attackers exploit this by placing malicious DLLs in directories that are searched before legitimate system directories, allowing them to inject code that executes with the privileges of the installer process.
The operational impact of this vulnerability extends beyond simple privilege escalation to encompass potential full system compromise and credential theft. When the vulnerable installer executes, it traverses the system PATH environment variable and loads DLLs without proper validation, creating a window where attackers can inject malicious code that operates at the same privilege level as the installer. This behavior directly maps to ATT&CK technique T1059.001 for execution through command-line interfaces and T1068 for privilege escalation. The vulnerability affects the entire installation lifecycle of the JPKI software, potentially allowing attackers to execute arbitrary code with elevated privileges, access sensitive cryptographic certificates, or manipulate the integrity of the certification service infrastructure. The attack vector is particularly concerning because it leverages the legitimate installation process itself, making detection more difficult and potentially bypassing security controls that monitor normal application execution.
Mitigation strategies for this vulnerability require immediate attention through multiple defensive layers. Organizations should implement strict directory permissions and access controls to prevent unauthorized DLL placement in system directories, while also enforcing application whitelisting policies that restrict which executables can run on the system. The most effective immediate solution involves updating to patched versions of the JPKI software where the installer properly validates and sanitizes search paths, ensuring that only trusted DLLs are loaded from predetermined secure directories. Security administrators should also monitor for suspicious file creation patterns in system directories and implement behavioral monitoring to detect when installer processes attempt to load DLLs from non-standard locations. Additionally, the principle of least privilege should be enforced during installation processes, limiting the capabilities of installer programs to reduce the potential impact of successful exploitation. This vulnerability underscores the critical importance of secure coding practices around PATH handling and dynamic library loading, particularly in installer components where elevated privileges are typically required to execute installation tasks.