Input Validation / Dll Hijacking



DLL Hijacking is a type of vulnerability where an attacker is able to gain control of a system by exploiting a DLL file. DLLs are dynamic link library files, which are executable files used by applications to perform certain tasks. A DLL hijacking attack involves a malicious actor crafting a specially crafted DLL file with the same name as a legitimate DLL file, and having it located in the same directory as the legitimate DLL file. When the vulnerable application is executed, the malicious DLL is loaded instead of the legitimate one, allowing the malicious actor to gain control of the vulnerable application. This vulnerability is classified in the Common Weakness Enumeration (CWE) directory as CWE-427: Uncontrolled Search Path Element. The OWASP Testing Guide also provides a comprehensive guide to testing for DLL hijacking vulnerabilities.


DLL hijacking is an incredibly dangerous vulnerability as it allows an attacker to gain complete control of a system. This can allow an attacker to install malicious software, steal confidential information, and more. A successful attack could have a major impact on an organization, leading to financial losses, reputational damage, and more. A risk assessment should be conducted to determine the risk posed by this vulnerability to the organization.


The best way to address a DLL hijacking vulnerability is to ensure that all DLL files are located in directories that are not accessible to potential attackers. Additionally, the application should be designed so that the DLLs are not loaded from any directory other than the one intended. This will help to prevent malicious actors from being able to craft malicious DLLs and have them loaded by the application.


The following example shows a vulnerable application that is vulnerable to a DLL hijacking attack. The vulnerable code is taken from CVE-2016-7255.

#include <windows.h>
#include <stdio.h>

int main()
    HMODULE hDLL = LoadLibrary("Example.dll");

    if (hDLL)
        printf("Loaded DLL\n");
        printf("Failed to load DLL\n");
    return 0;

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