In recent weeks, Google’s Threat Analysis Group’s (TAG) has observed multiple government-backed hacking groups exploiting the known vulnerability, CVE-2023-38831, in WinRAR, which is a popular file archiver tool for Windows. Cybercrime groups began exploiting the vulnerability in early 2023, when the bug was still unknown to defenders. A patch is now available, but many users still seem to be vulnerable. TAG has observed government-backed actors from a number of countries exploiting the WinRAR vulnerability as part of their operations.
To ensure protection, we urge organizations and users to keep software fully up-to-date and to install security updates as soon as they become available. After a vulnerability has been patched, malicious actors will continue to rely on n-days and use slow patching rates to their advantage. We also recommend use of Google’s Safe Browsing and Gmail, which block files containing the exploit.