Windows devices targeted by PuzzleMaker malware exploiting Chrome zero-day flaw
Chain of vulnerabilities used to attack multiple companies worldwide
According to reports, researchers first observed the attacks in mid-April. These attacks, which were highly targeted against companies worldwide, used a chain of Google Chrome and Microsoft Windows zero-day exploits.
Researchers failed to find an exploit used for remote code execution (RCE) in Chrome but found and analyzed an elevation-of-privilege exploit used to escape the sandbox and obtain system privileges.
Researchers said a user with the Twitter handle @r4j0x00 later published a working remote code execution exploit on GitHub.
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Following the use of this exploit, hackers then used another exploit to abuse Windows Notification Facility (WNF) with a Windows NTFS privilege escalation bug (CVE-2021-31956) to execute code with system privileges on compromised Windows 10 systems.
This enabled hackers to access the victim's system and execute four malware modules; these were stager, dropper, service, and remote shell modules.
The stager checks if exploitation is successful. If so, it downloads a dropper module from a C2 server. The dropper module installs two executables that pretend to be legitimate Windows files. The first file is registered as a service and used as a launcher for the second executable. The second file is used as a remote shell and is the attack's main payload.
"The remote shell module has a hardcoded URL of the C&C server inside (media-seoengine[.]com). All the communication between the C&C server and client is authorized and encrypted. The remote shell module is able to download and upload files, create processes, sleep for specified amounts of time and delete itself from the compromised machine," said researchers.
Researchers warned the malware doesn't appear to have any strong connections to other threat actors. Organizations have been urged to apply all patches to affected systems as soon as possible.
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