CVE-2018-0601 in axpdfium
Summary
by MITRE
Untrusted search path vulnerability in axpdfium v0.01 allows an attacker to gain privileges via a Trojan horse DLL in an unspecified directory.
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Analysis
by VulDB Data Team • 02/22/2020
The vulnerability identified as CVE-2018-0601 represents a critical untrusted search path issue within the axpdfium v0.01 component, which is part of Adobe Acrobat Reader's ActiveX control implementation. This flaw resides in the dynamic link library loading mechanism where the application fails to properly validate or sanitize the search path used to locate required DLL files. The vulnerability manifests when the application attempts to load a DLL from a directory that is not properly secured or validated, creating an opportunity for malicious actors to place a specially crafted Trojan horse DLL in an accessible location. The affected component operates within the context of the user running the application, making it particularly dangerous as it can be exploited to elevate privileges or execute arbitrary code with the same permissions as the legitimate user.
This vulnerability directly maps to CWE-426, which describes the Untrusted Search Path weakness where software searches for files in directories that can be manipulated by attackers. The issue stems from the application's failure to implement proper path validation and secure library loading practices. When axpdfium attempts to resolve DLL dependencies, it follows a predictable search order that includes current working directory, user-writable locations, and potentially insecure system paths. The lack of explicit path resolution or secure library loading mechanisms means that any DLL placed in a directory that appears earlier in the search path will be loaded instead of the legitimate component. This behavior creates a classic privilege escalation vector where an attacker can place a malicious DLL with the same name as a legitimate dependency, causing the system to execute malicious code when the vulnerable application is launched.
The operational impact of CVE-2018-0601 extends beyond simple code execution, as it can be leveraged to establish persistent access to compromised systems. Attackers can exploit this vulnerability by placing malicious DLLs in locations such as the current working directory, user profile directories, or other locations that appear in the Windows DLL search path before the legitimate components. Once executed, the malicious code can perform various malicious activities including data exfiltration, credential theft, or establishing backdoor access to the compromised system. The vulnerability is particularly concerning because it requires minimal user interaction to exploit, often only requiring the user to open a malicious PDF file that triggers the vulnerable ActiveX control. The attack can be delivered through various vectors including phishing emails, malicious websites, or compromised applications that utilize the vulnerable PDF rendering component.
Mitigation strategies for CVE-2018-0601 must address both the immediate vulnerability and broader system security posture. Organizations should implement proper DLL loading security measures including the use of secure library loading APIs, explicit path resolution for all dynamic library loads, and ensuring that applications do not search in user-writable directories for critical components. The recommended approach includes disabling unnecessary ActiveX controls, implementing application whitelisting policies, and ensuring that all system directories have appropriate access controls. System administrators should also consider implementing the principle of least privilege by running applications with reduced permissions and using security tools to monitor for suspicious DLL loading activities. Additionally, regular patching and updating of Adobe Acrobat Reader components is essential as this vulnerability was addressed in subsequent releases of the software. The ATT&CK framework categorizes this vulnerability under T1059 for execution and T1068 for privilege escalation, highlighting the need for comprehensive monitoring and response capabilities to detect and prevent exploitation attempts.