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Windows user-mode exploitation trick – refreshing the main process heap

During the weekend of May 21-23 (directly after the CONFidence CTF that we organized with Dragon Sector), qualifications to the famous DEF CON CTF 2016 took place. We obviously participated in what is probably the most binary heavy, challenging and competitive CTF of the year, eventually ending up 9th on the final scoreboard, which was sufficient […]

Details on a (not so recent now) stack-based buffer overflow in the Adobe CFF rasterizer in FreeType2 (CVE-2014-2240, CVE-2014-9659)

This blog has experienced a long time of inactivity, as I’ve recently used it only to publish slides from conferences I presented at, with many months-long breaks in between. I am planning to change things up and start posting again in the upcoming weeks, starting with this blog post, which I originally wrote in early 2014. I haven’t […]

Black Hat USA 2013, Bochspwn, slides and pointers

(Collaborative post by Mateusz “j00ru” Jurczyk and Gynvael Coldwind) Two weeks ago (we’re running late, sorry!) Gynvael and I had the pleasure to attend one of the largest, most technical and renowned conferences in existence – Black Hat 2013 in Las Vegas, USA. The event definitely stood up to our expectations – the city was purely […]

NoSuchCon’13 and crashing Windows with two instructions

The first edition of the NoSuchCon security conference held in Paris ended just a few days ago. Before anything else, I would like to thank all of the organizers (proudly listed at for making the event such a blast! Both the location, venue and speaker line-up were amazing, with lots of free beer and […]

A story of win32k!cCapString, or unicode strings gone bad

In the most recent blog post (“Fun facts: Windows kernel and guard pages”), we have learned how the code coverage of kernel routines referencing user-mode memory can be determined by taking advantage of the fact that kernel-mode code triggers guard page exceptions in the same way as user-mode does. Today, I will present how the […]

Fun facts: Windows kernel and guard pages

It has been a while since I last posted here, so I guess it’s high time to get back to work and share some more interesting Windows kernel internals goodies. Before we get to that, however, let’s start with a few announcements. First of all, there is a number of great infosec conferences coming up […]

Defeating Windows Driver Signature Enforcement #1: default drivers

One of the obvious things about the Windows operating system for anyone actively working on its kernel security is that the Driver Signature Enforcement (DSE in short) is not effective and can be bypassed with relative ease by any determined individual. From a historical perspective, the “feature” was introduced in the 64-bit build of Windows […]

0-day Windows XP SP3 Denial of Service (CSRSS Crash #1)

A rather short blog post today, as I am currently on my vacations. After publishing two, quite extensive write-ups regarding vulnerabilities in the Windows “CSRSS” component at Microsoft July Patch Tuesday: CVE-2011-1281: A story of a Windows CSRSS Privilege Escalation vulnerability CVE-2011-1282: User-Mode NULL Pointer Dereference & co. I would like to shortly discuss the […]

CVE-2011-1281: A story of a Windows CSRSS Privilege Escalation vulnerability

Today, I would like to present a detailed description of the CVE-2011-1281 vulnerability [1], which was reported by me several months ago and patched today, together with four other bugs marked as the Elevation of Privileges class, on the occasion of the monthly Microsoft Patch Tuesday cycle (see Microsoft Security Bulletin MS11-056, a summary of […]

PE Import Table and custom DLL paths

Once upon a time, an interesting software vulnerability vector called DLL Hijacking became very popular, thanks to a Slovenian security research outfit – ACROS Security, as well as HD Moore and his DLL Hijacking Audit Kit. In short, the vulnerability class allowed an attacker to execute arbitrary code in the context of an application, which […]