Exploit
From Discovery to Disclosure: ReCrystallize Server Vulnerabilities
TL&DR – While on an assessment, I found an instance of ReCrystallize Server. It had many problems, some of which had to do with insufficient hardening on the client’s side while others were new vulnerabilities I found that when chained together, achieve Remote Code Execution (RCE). These vulnerabilities were disclosed to ReCrystallize Software and MITRE. Besides the disclosed vulnerabilities, some “features” were also used for malicious purposes. The replication and…
Sail away, sail away, sail away
A while back, after some live music and drinks at Railways, I made my way to another city for pleasant weather, some dubious food, the ever-wakeful seagulls, and ultimately – an assessment. After playing around for a few days, Jason and I had obtained access to a system which contained cleartext credentials, namely ihsadmin:ihsadmin. Using these credentials, we were also able to SSH into a management server of sorts. While…
The power of variant analysis (Semmle QL) CVE-2019-15937 and CVE-2019-15938
This post will try to do a small introduction to the QL language using real-world vulnerabilities that I found in the past, and it will end with a small challenge using QL. A few months ago, I heard of Semmle QL for the first time, what they do is perform multiple code analysis techniques against source code, and dump these results into a database. Then using the QL language, you…
Analysis of a 1day (CVE-2019-0547) and discovery of a forgotten condition in the patch (CVE-2019-0726) – Part 1 of 2
This post will cover my journey into the analysis of CVE-2019-0547 (Affecting the windows DHCP client), a vulnerability discovered by Mitch Adair of Microsoft Windows Enterprise Security Team and how I found a new issue in the same function. Part 1Patch extractionPatch diffingProgram flow to the functionDHCP Options0x000x00Part 2Integer overflowNobody respects RFCs0xC0 “compression algorithm”Final conclusions Even though these first steps around patch downloading, extraction and diffing are already heavily documented…
Being Stubborn Pays Off pt. 1 – CVE-2018-19204
During an internal assessment, I came across monitoring software that had default credentials configured. This monitoring software allowed for the creation of sensors, but, none of which would allow for code execution or any other things that could compromise an underlying system. Turns out, it was a vulnerable version based on a publicly known CVE, but there was no public exploit code. Join me in this quest on building an…
Linux Heap Exploitation Intro Series: Set you free() – part 2
Hello there! On this part we are focusing on abusing chunk creation and heap massaging in hope of overwriting the __malloc_hook weak pointer. Before getting into all the juicy stuff let’s remember some key things from last post. The value returned by png_get_uint_32 is of type unsigned integer For a 32 bit integer, the following happens: 0xffffffff + 1 = 0 fread will read values into the destination unless it can’t read from source…
Linux Heap Exploitation Intro Series: Set you free() – part 1
Hello and welcome to the final post of our Intro to exploitation series! We have learned the basics about how the memory management as per the ptmalloc2 allocator works. It was a basic but enough approach to have a good starting point. However, there are a few concepts and attack scenarios that, due to existing a lot of information about these, I have kept long distance from “unsafe unlink“, “malloc (des)malleficarum” and…
Linux Heap Exploitation Intro Series: Riding free on the heap – Double free attacks!
Hello again and welcome to the third of our series. On today’s blog post we are going to see what is and how can we abuse a double free(). We are also going to take advantage of leaks that happen when doing double free()‘s and see some examples of code execution using said leaks – we are making our execution ride on frees! As a last note, we are going to…
Outlook Home Page – Another Ruler Vector
Ruler has become a go to tool for us on external engagements, easily turning compromised mailbox credentials into shells. This has resulted in security being pushed forward and Microsoft responding with patches for the two vectors used in Ruler, namely rules and forms. These were patched with KB3191938 and KB4011091 respectively. This puts us back into the cat and mouse game of attack versus defence, with attack needing to find a new vector.…
Macro-less Code Exec in MSWord
Authors: Etienne Stalmans, Saif El-Sherei What if we told you that there is a way to get command execution on MSWord without any Macros, or memory corruption?! Windows provides several methods for transferring data between applications. One method is to use the Dynamic Data Exchange (DDE) protocol. The DDE protocol is a set of messages and guidelines. It sends messages between applications that share data and uses shared memory to…
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