CVE-2021-42711: 
Barracuda Network Access Client vulnerability analysis and mitigation

Barracuda Network Access Client (NAC/VPN) for Windows contained a local privilege escalation vulnerability prior to version 5.2.2. The vulnerability was discovered in October 2021 and was assigned CVE-2021-42711. The issue affects all versions of Barracuda Network Access Client before version 5.2.2 (Mandiant Advisory).

The vulnerability stems from insecure file operations during the repair process of the Windows Installer framework. When the agent is installed, an MSI file is cached in c:\windows\installer. During a repair operation, which can be triggered by an unprivileged user either through the Windows Installer API or by running 'msiexec.exe /fa c:\windows\installer[XXXXX].msi', several file operations are performed in the user's %TEMP% folder. Some of these operations, including the execution of temporary files, are performed with SYSTEM privileges (Mandiant Advisory). The vulnerability has been assigned a CVSS base score of 7.2 HIGH (NVD).

The vulnerability has a high impact as successful exploitation grants SYSTEM level privileges to a local unprivileged attacker. This effectively allows any authenticated local user to escalate their privileges to the highest level on the system (Mandiant Advisory).

The vulnerability was fixed in Barracuda Network Access Client version 5.2.2, released on November 24, 2021. Users should update to this version or later to address the vulnerability (Mandiant Advisory).