Computest Sector 7 was asked by Team High-Tech Crime of the Dutch Police to help with writing a decryptor for the DoNex/DarkRace ransomware. DoNex is a relatively new ransomware group, which probably explains why its encryptor contains a simple to abuse mistake. It appears to be the same group that was working under the name DarkRace last year, as the DoNex encryptor we investigated is essentially the same as a DarkRace encryptor we looked at.
In the Patch Tuesday update of April 2024, Microsoft released a fix for CVE-2024-20693, a vulnerability we reported. This vulnerability allowed manipulating the cached signature signing level of an executable or DLL. In this post, we’ll describe how we found this issue and what the impact could be on Windows 11. Background Last year, we started a project to improve our knowledge of Windows internals, specifically about local vulnerabilities such as privilege escalation.
In a previous blog post we described a process injection vulnerability affecting all AppKit-based macOS applications. This research was presented at Black Hat USA 2022, DEF CON 30 and Objective by the Sea v5. This vulnerability was actually the second universal process injection vulnerability we reported to Apple, but it was fixed earlier than the first. Because it shared some parts of the exploit chain with the first one, there were a few steps we had to skip in the earlier post and the presentations.
In this blog post, we’ll describe a design issue in the way XPC connections are authorised in Apple’s operating systems. This will start by describing how XPC works and is implemented on top of mach messages (based on our reverse engineering). Then, we’ll describe the vulnerability we found, which stems from implementing a (presumed to be) one-to-one communication channel on top of a communication channel that allows multiple concurrent senders. Next, we’ll describe this issue using an example for smd and diagnosticd on macOS.
Microsoft has published a patch for CVE-2023-38146 on patch Tuesday of September 2023. The advisory for this vulnerability mentions that the impact is remote code execution, which was demonstrated by @carrot_c4k3 - the researcher who first reported the vulnerability to Microsoft in May of 2023. Her ThemeBleed writeup and proof-of-concept demonstrate how an attacker might exploit the vulnerability for code execution by luring an unsuspecting victim into opening a booby-trapped .
For the last couple of weeks we’ve assisted the Dutch police in investigating the Genesis Market. In case you are unfamiliar with this market, it was used to sell stolen login credentials, browser cookies and online fingerprints (in order to prevent ‘risky sign-in’ detections), by some referred to as IMPaas, or Impersonation-as-a-Service. The market seemed to have started in 2018 and its activities have resulted in approximately two million victims. If you want to know more about this operation, you can read our other blog post.
Code signing of applications is an essential element of macOS security. Besides signing applications, it is also possible to sign installer packages (.pkg files). During a short review of the xar source code, we found a vulnerability (CVE-2022-42841) that could be used to modify a signed installer package without invalidating its signature. This vulnerability could be abused to bypass Gatekeeper, SIP and under certain conditions elevate privileges to root.