WinRAR, an over 20-year-old file archival utility used by over 500 million users worldwide, recently acknowledged a long-standing vulnerability in its code-base. A recently published path traversal zero-day vulnerability, disclosed in CVE-2018-20250 by Check Point Research, enables attackers to specify arbitrary destinations during file extraction of ‘ACE’ formatted files, regardless of user input. Attackers can easily achieve persistence and code execution by creating malicious archives that extract files to sensitive locations, like the Windows “Startup” Start Menu folder. While this vulnerability has been fixed in the latest version of WinRAR (5.70), WinRAR itself does not contain auto-update features, increasing the likelihood that many existing users remain running out-of-date versions.
FireEye has observed multiple campaigns leveraging this vulnerability, in addition to those already discussed by 360 Threat Intelligence Center. Below we will look into some campaigns we came across that used customized and interesting decoy documents with a variety of payloads including ones which we have not seen before and the ones that used off-the-shelf tools like PowerShell Empire.