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CVE-2015-0050: Microsoft Internet Explorer 8 MSHTML SRunPointer::SpanQualifier/RunType OOB read details

Throughout November, I plan to release details on vulnerabilities I
found in web-browsers which I've not released before. This is the
sixteenth entry in that series. Unfortunately I won't be able to
publish everything within one month at the current rate, so I may
continue to publish these through December and January.

The below information is available in more detail on my blog at
http://blog.skylined.nl/20161122001.html. There you can find a repro
that triggered this issue in addition to the information below.

Follow me on http://twitter.com/berendjanwever for daily browser bugs.

MSIE 8 MSHTML SRunPointer::SpanQualifier/RunType OOB read
(MS15-009, CVE-2015-0050)

A specially crafted web-page can cause Microsoft Internet Explorer 8 to
attempt to read data beyond the boundaries of a memory allocation. The
issue does not appear to be easily exploitable.

Known affected software, attack vectors and mitigations
* Microsoft Internet Explorer 8

  An attacker would need to get a target user to open a specially
  crafted web-page. Disabling Javascript should prevent an attacker
  from triggering the vulnerable code path.

The issue requires rather complex manipulation of the DOM and results in
reading a value immediately following an object. The lower three bits of
this value are returned by the function doing the reading, resulting in
a return value in the range 0-7. After exhaustively skipping over the
read AV and having that function return each value, no other side
effects were noticed. For that reason I assume this issue is hard if not
impossible to exploit and did not investigate further. It is still
possible that there may be subtle effects that I did not notice that
allow exploitation in some form or other.

* *June 2014*: This vulnerability was found through fuzzing.
* *October 2014*: This vulnerability was submitted to ZDI.
* *October 2014*: This vulnerability was rejected by ZDI.
* *November 2014*: This vulnerability was reported to MSRC.
* *February 2015*: This vulnerability was addressed by Microsoft in
* *November 2016*: Details of this issue are released.



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