This module exploits a use-after-free vulnerability that currents
targets Internet Explorer 9 on Windows 7, but the flaw should exist in
versions 6/7/8/9/10/11. It was initially found in the wild in Japan, but
other regions such as English, Chinese, Korean, etc, were targeted as
well.
The vulnerability is due to how the mshtml!CDoc::SetMouseCapture function
handles a reference during an event. An attacker first can setup two
elements, where the second is the child of the first, and then setup a
onlosecapture event handler for the parent element. The onlosecapture
event seems to require two setCapture() calls to trigger, one for the parent
element, one for the child. When the setCapture() call for the child element
is called, it finally triggers the event, which allows the attacker to cause
an arbitrary memory release using document.write(), which in particular frees
up a 0x54-byte memory. The exact size of this memory may differ based on the
version of IE. After the free, an invalid reference will still be kept and pass
on to more functions, eventuall this arrives in function
MSHTML!CTreeNode::GetInterface, and causes a crash (or arbitrary code execution)
when this function attempts to use this reference to call what appears to be a
PrivateQueryInterface due to the offset (0x00).
To mimic the same exploit found in the wild, this module will try to use the
same DLL from Microsoft Office 2007 or 2010 to leverage the attack.
According to the Ruby style guide, %w{} collections for arrays of single
words are preferred. They're easier to type, and if you want a quick
grep, they're easier to search.
This change converts all Payloads to this format if there is more than
one payload to choose from.
It also alphabetizes the payloads, so the order can be more predictable,
and for long sets, easier to scan with eyeballs.
See:
https://github.com/bbatsov/ruby-style-guide#collections
This module exploits a use-after-free vulnerability found in Internet Explorer,
specifically in how the browser handles the caret (text cursor) object. In IE's
standards mode, the caret handling's vulnerable state can be triggered by first
setting up an editable page with an input field, and then we can force the caret
to update in an onbeforeeditfocus event by setting the body's innerHTML property.
In this event handler, mshtml!CCaret::`vftable' can be freed using a document.write()
function, however, mshtml!CCaret::UpdateScreenCaret remains unaware aware of this
change, and still uses the same reference to the CCaret object. When the function
tries to use this invalid reference to call a virtual function at offset 0x2c, it
finally results a crash. Precise control of the freed object allows arbitrary code
execution under the context of the user.
The vuln works against IE8 on Win 7, but the current version of the custom spray
doesn't actually work well against that target. More work is needed before we can
add that target for sure. The reason a custom spray is needed is because the
document.write() function erases the typical spray routines we use like
js_property_spray, or the heaplib + substring one. Tried using an iframe too,
but onbeforeeditfocus event doesn't seem to work well in an iframe (does not
fire when innerHTML is used.)
In IE8 standards mode, it's possible to cause a use-after-free condition by first
creating an illogical table tree, where a CPhraseElement comes after CTableRow,
with the final node being a sub table element. When the CPhraseElement's outer
content is reset by using either outerText or outerHTML through an event handler,
this triggers a free of its child element (in this case, a CAnchorElement, but
some other objects apply too), but a reference is still kept in function
SRunPointer::SpanQualifier. This function will then pass on the invalid reference
to the next functions, eventually used in mshtml!CElement::Doc when it's trying to
make a call to the object's SecurityContext virtual function at offset +0x70, which
results a crash. An attacker can take advantage of this by first creating an
CAnchorElement object, let it free, and then replace the freed memory with another
fake object. Successfully doing so may allow arbitrary code execution under the
context of the user.
This bug is specific to Internet Explorer 8 only. It was originally discovered by
Orange Tsai at Hitcon 2013, but was silently patched in the July 2013 update, so
no CVE as of now.
jvazquez-r7