Wednesday, 14 September 2016

Microsoft Windows PDF Library Information Disclosure Vulnerability - CVE-2016-3374 (MS16-115)

In the last year, as a personal research project, I started to look more into browsers and decided to fuzz some high-level targets, such as Edge and IE11, together with Steven Seeley (@steventseeley).

I have to admit that it is quite hard nowadays to approach this kind of research, especially with limited time and resources (just few virtual machines running at home…), but nevertheless it became an incredible learning experience.

Given our constraints, the fuzzing focus was to target other things than common targeted components, such as DOM, JavaScript and so on, so we decided to go for the PDF file format.

One of the interesting conditions that we found was the one that has just been patched by Microsoft and detailed in the MS16-115 security bulletin. The vulnerability is an out-of-bounds read which can lead to memory information disclosure.

The technical advisory can be found at Steven Seeley's web site: http://srcincite.io/advisories/src-2016-39/ .

References:

- Microsoft Security Bulletin MS16-115: https://technet.microsoft.com/library/security/MS16-115
- SRC-2016-39 : Microsoft Windows PDF Library PostScript Calculator Out-of-Bounds Read Information Disclosure Vulnerability: http://srcincite.io/advisories/src-2016-39/
- Microsoft Acknowledgments: https://technet.microsoft.com/library/security/mt674627.aspx