Researchers have discovered a malspam campaign that is distributing a a malicious RAR archive that may be the first one to exploit the newly discovered WinRAR ACE vulnerability to install malware on a computer.
Last week, Checkpoint disclosed a 19 year old vulnerability in the WinRAR UNACEV2.DLL library that allows a specially crafted ACE archive to extract a file to the Window Startup folder when it is extracted. This allows the executable to gain persistence and launch automatically when the user next logs in to Windows.
As the developers of WinRAR no longer have access to the source code for the vulnerable UNACEV2.DLL library, instead of fixing the bug, they removed the DLL and ACE support from the latest version of WinRAR 5.70 beta 1. While this fixes the vulnerability, it also removes all ACE support from WinRAR.
Unfortunately, this does not help the approximately 500 million users who allegedly have WinRAR installed on their computers and that is exactly what malware developers are banking on.
Today, 360 Threat Intelligence Center tweeted that they have discovered an email that was distributing a RAR archive that when extracted will infect a computer with a backdoor.