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DLL Hijacking Vulnerability

DLL (Dynamic Link Library) Hijacking is a technique utilized by attackers to execute malicious code on a system by exploiting vulnerabilities in applications that improperly load DLL files. By placing a malicious DLL file in a location where a vulnerable application searches for DLL dependencies, an attacker can hijack the application's execution flow and potentially escalate privileges or perform unauthorized actions.

Understanding DLL Hijacking

When an application dynamically loads DLL files during runtime, it searches specific directories to locate these DLL dependencies. If the application's search path includes writable or insecure directories, an attacker can place a malicious DLL file with the same name as one of the expected dependencies. When the vulnerable application is executed, it inadvertently loads the attacker-controlled DLL instead of the legitimate one, enabling the execution of malicious code.

Exploitation Using Procmon.exe

DLL Hijacking: DLL Hijacking

The screenshot illustrates the process of DLL hijacking using Procmon.exe. The vulnerable application, in this case, the Damm Vulnerable Thick Client App (DVTA), attempts to load a DLL file from a specific path, which is missing. An attacker can exploit this vulnerability by creating the necessary folder structure and placing a malicious DLL file with the expected name. Upon execution of the DVTA, the malicious DLL is loaded, allowing the attacker to escalate privileges or execute arbitrary code.

Mitigation Strategies

To mitigate DLL hijacking vulnerabilities, consider the following measures:

  • Secure DLL Loading: Applications should employ secure loading mechanisms, such as specifying absolute paths or using cryptographic hash verification to ensure the integrity of loaded DLLs.

  • Reduce Search Paths: Minimize the search paths for DLL loading to only include trusted directories and avoid searching in insecure locations.

  • Code Signing: Digitally signing DLL files can help verify their authenticity and prevent tampering.

  • Regular Updates: Keep applications and system components up-to-date to patch known vulnerabilities and mitigate potential risks.