In June 2022, Microsoft patched a significant vulnerability in its Windows operating system kernel, tracked as CVE-2022-30162. This flaw allowed low-privileged users to gain access to sensitive kernel memory data they are not supposed to see, potentially enabling attackers to further undermine the system's security. In this post, we’ll break down how CVE-2022-30162 works, examine code snippets that illustrate the vulnerability, share details on possible exploitation, and suggest ways to stay safe.

What is CVE-2022-30162?

At its core, CVE-2022-30162 is an _information disclosure_ bug in the Windows Kernel. It affects Windows 10, Windows 11, and several Windows Server editions. Successful exploitation can allow an attacker to read parts of kernel memory, which can contain passwords, cryptographic keys, security tokens, or pointers helpful for further attacks like privilege escalation.

The vulnerability was rated "Important" with a CVSS base score of 5.5. While not as severe as remote code execution flaws, information disclosure bugs often play a crucial role in sophisticated attacks by helping adversaries bypass kernel Address Space Layout Randomization (KASLR) and other protections.

How Does the Vulnerability Work?

Let’s simplify things: the Windows Kernel is the “heart” of the operating system, managing communications between software and hardware. Normally, Windows restricts what information a regular user process can learn about the kernel’s internal workings. However, due to this vulnerability, certain system calls (APIs exposed by the kernel) could reveal more data than intended.

Specifically, the problem was caused by insufficient memory initialization in kernel-mode functions. When structures allocated in kernel memory were copied to user-mode, parts of these structures remained uninitialized. As a result, attackers could request these structures and receive memory fragments filled with leftover data (“kernel memory leaks”).

Code Example: Triggering the Vulnerability

One classic example of this type of bug involves calling Windows APIs like NtQuerySystemInformation or device drivers returning kernel-allocated memory to user mode.

Here’s a simple C code snippet that illustrates how an attacker might try to access the leaked memory (this particular snippet is for educational purposes only):

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

typedef NTSTATUS(WINAPI* _NtQuerySystemInformation)(
    ULONG SystemInformationClass,
    PVOID SystemInformation,
    ULONG SystemInformationLength,
    PULONG ReturnLength
);

int main() {
    HMODULE ntdll = LoadLibraryA("ntdll.dll");
    _NtQuerySystemInformation NtQuerySystemInformation = 
        (_NtQuerySystemInformation)GetProcAddress(ntdll, "NtQuerySystemInformation");

    DWORD bufSize = x10000;
    BYTE* buffer = (BYTE*)malloc(bufSize);

    ULONG outLen = ;
    NTSTATUS status = NtQuerySystemInformation(x20, buffer, bufSize, &outLen);

    if (status == ) {
        printf("Data received from kernel.\nSample bytes:\n");
        for (size_t i = ; i < 64; ++i)
            printf("%02x ", buffer[i]);
        printf("\n");
    } else {
        printf("Query failed. Status: x%08lx\n", status);
    }

    free(buffer);
    FreeLibrary(ntdll);

    return ;
}

The code calls a native Windows API to get information from the kernel.

- If the kernel returns uninitialized memory, the buffer may now include fragments of leftover kernel data.

What can an attacker do with this bug?

- Leak Kernel Addresses: By mapping out precise memory regions, attackers can defeat KASLR, making further kernel exploits easier.
- Steal Sensitive Data: Leaked memory could contain cryptographic material or security tokens, aiding in lateral movement or privilege escalation.
- Build Exploit Chains: Although info leaks aren’t directly weaponizable, they are vital pieces in chaining together full exploits.

Limitations:

Proof of Concept & Real-World Exploitation

While no public worms have exploited this bug, security researchers have shown how such info leaks can increase the reliability of kernel privilege escalation exploits.

For example, similar kernel leaks have enabled the exploitation of other vulnerabilities that would otherwise require brute-forcing or guesswork.

Microsoft’s Patch and Recommendations

Microsoft fixed this bug by ensuring that all kernel structures are completely padded and zeroed before being handed to user-mode processes:

- Microsoft Security Update Guide: CVE-2022-30162
- June 2022 Patch Tuesday Report

What you should do

- _Update your Windows operating system_ as soon as possible. The patch is included in June 2022 cumulative updates.

Conclusion

CVE-2022-30162 serves as a prime example of how “innocent-looking” bugs in the Windows Kernel can have severe security consequences. Even if a bug doesn’t let hackers directly seize control, leaking internal secrets can open the door for larger, more damaging attacks.

Remember: Staying up to date with security patches and understanding the risks of information disclosure vulnerabilities is essential for keeping your systems safe. If you are a developer writing system-level code, always make sure to initialize your memory buffers!

References

- CVE-2022-30162 - Microsoft Security Response Center
- June 2022 Windows Updates Overview (Bleeping Computer)
- Google Project Zero – The Importance of Infoleaks

Timeline

Published on: 06/15/2022 22:15:00 UTC
Last modified on: 06/25/2022 03:16:00 UTC