CVE-2018-0624 in Kaikei
Summary
by MITRE
Untrusted search path vulnerability in Multiple Yayoi 17 Series products (Yayoi Kaikei 17 Series Ver.23.1.1 and earlier, Yayoi Aoiro Shinkoku 17 Ver.23.1.1 and earlier, Yayoi Kyuuyo 17 Ver.20.1.4 and earlier, Yayoi Kyuuyo Keisan 17 Ver.20.1.4 and earlier, Yayoi Hanbai 17 Series Ver.20.0.2 and earlier, and Yayoi Kokyaku Kanri 17 Ver.11.0.2 and earlier) allows an attacker to gain privileges via a Trojan horse DLL in an unspecified directory. This flaw exists within the handling of ykkapi.dll loaded by the vulnerable products.
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Analysis
by VulDB Data Team • 10/04/2025
The vulnerability identified as CVE-2018-0624 represents a critical untrusted search path issue affecting multiple products within the Yayoi Kaikei 17 Series and related software applications. This flaw manifests in versions of Yayoi Kaikei 17 Series Ver.23.1.1 and earlier, along with several other products in the Yayoi 17 Series including Aoiro Shinkoku 17, Kyuuyo 17, Kyuuyo Keisan 17, Hanbai 17, and Kokyaku Kanri 17, all of which are susceptible to privilege escalation through malicious DLL loading mechanisms. The vulnerability specifically impacts the handling of ykkapi.dll which serves as a critical component in the software architecture and creates an attack surface where malicious actors can manipulate the system's dynamic link library loading process.
The technical implementation of this vulnerability stems from improper handling of dynamic link library loading sequences within the affected software products. When these applications execute, they traverse a search path that includes unspecified directories where untrusted DLL files might reside. The ykkapi.dll component is loaded without proper validation of its source or integrity, allowing an attacker to place a malicious Trojan horse DLL in a directory that gets searched before the legitimate system directories. This creates a classic DLL hijacking scenario where the system loads the attacker-controlled library instead of the intended legitimate one, enabling privilege escalation and potential system compromise.
From an operational perspective, this vulnerability presents significant risks to organizations using these specific versions of Yayoi software products, particularly in financial and accounting environments where these applications handle sensitive business data. The privilege escalation capability means that an attacker who successfully exploits this vulnerability could gain elevated system privileges, potentially leading to complete system compromise, data exfiltration, or persistent backdoor access. The unspecified directory nature of the search path makes it particularly challenging to defend against as attackers can place malicious DLLs in various locations within the system's path traversal sequence.
The vulnerability aligns with CWE-427 Uncontrolled Search Path Element, which specifically addresses situations where software searches for files using paths that can be manipulated by attackers. This weakness is further categorized under ATT&CK technique T1059 Command and Scripting Interpreter and T1068 Exploitation for Privilege Escalation, demonstrating how attackers can leverage such flaws to achieve their objectives. Organizations should consider this vulnerability as part of a broader attack surface assessment, particularly when these applications are deployed in environments with limited security controls or when users have the ability to modify system directories. The attack vector is particularly concerning in environments where users might have write permissions to directories that are part of the application's search path, creating a direct pathway for exploitation.
Mitigation strategies for CVE-2018-0624 should focus on immediate software updates to versions that address the untrusted search path handling issue. Organizations should implement strict directory permissions and access controls to prevent unauthorized DLL placement in critical system directories. The application should be configured to use absolute paths for DLL loading rather than relying on the system search path, and security monitoring should be enhanced to detect suspicious file placement activities. Additionally, network segmentation and application whitelisting policies can provide additional defense layers to prevent exploitation attempts, while regular security audits should verify that no malicious DLLs have been placed in the affected search paths.