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CoreLabs Articles

Read articles from CoreLabs, the research division of Core Security. CoreLabs prides itself on taking a holistic view of information security with a focus on developing solutions to complex, real-world security problems that affect our customers.


We are thrilled to announce a new version of Impacket! After months of hard work and dedication, Impacket v0.11.0 is now available and has a bunch of new and exciting features. We can’t wait for you to explore and enjoy the added capabilities that come with this version! Let’s take a look at everything new included in this release.
Recently, the Nokoyawa ransomware group, which has been active since In February 2022, was found to be exploiting a Windows zero-day vulnerability in one of its attacks. This vulnerability targets the Common Log File System (CLFS) and allows attackers to escalate privileges and potentially fully compromise an organization’s Windows systems. In April 2023, Microsoft released a patch for this vulnerability and the CNA CVE-2023-28252 was assigned.
In this article we would like to share the analysis and work done on CVE-2022-37969 to build a functional PoC based on previously published information by Zscaler.
In part 14, we began discussing how to analyze the difficulty of creating a rop depending on the scenario. In this part, we’ll continue that discussion with a rop that is not as simple as the ones we have seen in previous parts. As we did last time, we’ll start by using radare in visual mode to practice. Reversing with Radare, Exercise 2: 32 Bits As a reminder, the exercises are available here:
In part 13, we analyzed and adapted the RESOLVER for 64 bits. In this part, we’ll discuss how to analyze the difficulty of creating a rop depending on the scenario.
When we think about EDR or AV evasion, one of the most widespread methods adopted by offensive teams is the use of system calls (syscalls) to carry out specific actions. This technique is so common and effective simply because most AVs/EDR have userland hooks to track and intercept requests userland processes make. However, we found that a key userland API, CreateProcess, is still extensively used even in offensive tools to create processes.
I wanted to write this article to demonstrate the analysis I did while developing the Core Impact exploit “Windows Network File System Remote” that abuses the CVE-2022-30136 vulnerability.
The F5 BIG-IP iControl REST vulnerability, a critical authentication bypass vulnerability that leads to unauthenticated remote code execution, is quite simple to exploit and provides an attacker with a method to execute arbitrary system commands as root.
In this blogpost, we’ll briefly describe how we developed a DoS module for CVE-2022-21907. Instead of viewing it in a result-oriented way, we’ll approach it from a research standpoint, describing the process of developing this module for Core Impact.
In part 12, we completed the ROP bypass of the DEP in 64 bits. In this part, we’ll analyze and adapt the RESOLVER for 64 bits.  Resolution of the 64-Bit Exercise As a quick point of clarification, the shellcode is not mine. However, it is quite public, so it was simply adapted for this example.
I wanted to write this blog to show the analysis I did in the context of developing the Core Impact exploit “Win32k Window Object Type Confusion” that abuses the CVE-2022-21882 vulnerability. It’s based on the existing Proof of Concept (POC), which is both interesting and quite complex.
In part 11, we completed the ROP bypass of the DEP. In this part, we’ll begin our first exercise compiled in 64 bits. Before beginning, we’ll go over a few concepts in detail, because this exercise requires a new frame of reference. While the base is the same, it’s important to know the differences between 32 and 64 bits in order to be successful in reversing.
This post focuses on creating Cobalt Strike Beacon Object Files using the MinGW compiler on Linux. We will discuss several ideas and best practices that will increase the quality of your BOFs. Flexibility Compiling to Both Object Files and Executables While writing a BOF is great, it’s always worth making the code compile to both BOF and EXE.
The Log4Shell vulnerability, a serious remote code execution vulnerability in the Apache Log4j2 library, is one of the best candidates for winning several Pwnie awards in 2022.
In part 10, we started exploring different protections and mitigations that we may find. In this part, we’ll continue this exercise, completing the ROP bypass of the DEP. Roping Step by Step Typically, there are tools that, in simple cases can automatically build a ROP. However, in difficult cases, these tools generally can’t fully build one, or can only partially do so, leaving one to complete by hand the work that the tool could not do.
In the previous parts of this series, we went through some basic examples of exploitation and reversing. Now we’ll take a step forward, gradually adding different protections and mitigations that we will find.
In part 8, we solved ABO3 using IDA FREE. In this part, we’ll use Radare to solve ABO4. Updating Radare and Cutter First, we’ll need to update to the new version of Cutter, the Radare GUI. A pop-up will prompt us to update whenever there is a new version:
CVE-2021-26897 is a DNS server RCE vulnerability, and is triggered when many consecutive Signature RRs Dynamic Updates are sent. This vulnerability is an OOB write on the heap when combining the many consecutive Signature RR Dynamic Updates into base64-encoded strings before writing to the Zone file.
In part 7, we solved ABO2 in GHIDRA. In this part, we’ll use IDA FREE to solve ABO3. As is the case with all of the ABOS, the goal is to run the calculator or some other executable that we want. 
The new format of Microsoft monthly updates have proven challenging to reverse engineer. We’ve figured out a workaround that we hope will be helpful. In the original format, the Microsoft updates have always included the full files to patch, and from there it’s relatively straightforward to work on reversing and diffing through only extracting, without installing the patch.
Ransomware, as an active variant of current malware, has undoubtedly undergone a series of changes that have allowed cyber criminals to expand the horizons of clandestine business. In order to try to understand the different "forms" ransomware has presented over time, this article will show the evolutionary line of this latent threat in a compact and concrete way.
Authored by: Ernesto Alvarez, Senior Security Consultant, Security Consulting Services This article describes techniques used for creating UDP redirectors for protecting Cobalt Strike team servers. This is one of the recommended mechanisms for hiding Cobalt Strike team servers and involves adding different points which a Beacon can contact for instructions when using the HTTP channel.
The pen testing world is constantly changing and threat actors are continually finding new ways to exploit organizations of all industries and sizes. In order for pen testers to safely and efficiently test and expose security weaknesses, they enlist the help of different tools. This article series from cybersecurity expert Ricardo Narvaja provides tips and tricks on reversing and exploiting Windows using free and easy to get tools.
In part 6, we learned how to understand a shellcode and its resolver. Now, we will continue with the analysis and resolution of abo2 in GHIDRA. Download ABO2 executable. The latest version is on Google drive.