CVE-2017-7327 in Browser installer for Desktop
Summary
by MITRE
Yandex Browser installer for Desktop before 17.4.1 has a DLL Hijacking Vulnerability because an untrusted search path is used for dnsapi.dll, winmm.dll, ntmarta.dll, cryptbase.dll or profapi.dll.
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Analysis
by VulDB Data Team • 12/25/2019
The CVE-2017-7327 vulnerability represents a critical DLL hijacking flaw in the Yandex Browser installer for desktop systems prior to version 17.4.1. This vulnerability stems from the installer's improper handling of dynamic link library loading mechanisms, creating exploitable conditions that allow malicious actors to execute arbitrary code with elevated privileges. The flaw specifically affects the installer's search path resolution process, where it fails to properly validate or restrict the locations from which required system libraries are loaded.
The technical implementation of this vulnerability involves the installer's reliance on an untrusted search path for critical system DLLs including dnsapi.dll, winmm.dll, ntmarta.dll, cryptbase.dll, and profapi.dll. When the installer attempts to load these libraries, it follows a predictable search order that includes the current working directory and other user-controllable locations before checking the system directories. This behavior creates opportunities for attackers to place malicious versions of these DLLs in strategic locations, which the installer will then load and execute without proper validation or authentication mechanisms.
This vulnerability operates at the intersection of multiple cybersecurity domains and aligns with CWE-426, which specifically addresses Untrusted Search Path vulnerabilities. The operational impact of this flaw extends beyond simple privilege escalation, as it enables attackers to gain system-level control through the installation process itself. The attack surface is particularly concerning because it targets the installer phase, which typically runs with elevated privileges, making successful exploitation potentially devastating for affected systems. The vulnerability also relates to ATT&CK technique T1059.001, which covers Command and Scripting Interpreter, as attackers can leverage the hijacked DLLs to execute malicious code within the context of the installer process.
The implications of this vulnerability are significant for enterprise environments where software deployment processes are common and often automated. Attackers can exploit this weakness by placing malicious DLLs in directories that are searched before system directories, effectively hijacking the legitimate installation process. This creates a persistent threat vector that can be leveraged for privilege escalation, lateral movement, and potentially full system compromise. The vulnerability affects not only individual users but also organizations that rely on automated deployment mechanisms for software distribution, as the installer process may be invoked with elevated privileges during normal operations.
Organizations should implement immediate mitigations including updating to Yandex Browser version 17.4.1 or later, which addresses the untrusted search path issue through proper library loading mechanisms. System administrators should also implement additional controls such as monitoring for suspicious DLL loading patterns, restricting write access to installer directories, and employing application whitelisting policies to prevent unauthorized DLL placement. The vulnerability demonstrates the critical importance of proper library loading practices and highlights the need for robust input validation and secure coding practices in installation and deployment processes. Security teams should also consider implementing behavioral monitoring solutions that can detect anomalous DLL loading patterns that may indicate exploitation attempts.