High [CVE-2021-26887] Microsoft Windows Folder Redirection Elevation of Privilege Vulnerability

An elevation of privilege vulnerability exists in Microsoft Windows when Folder redirection has been enabled via Group Policy. When folder redirection file server is co-located with Terminal server, an attacker who successfully exploited the vulnerability would be able to begin redirecting another user's personal data to a created folder.

To exploit the vulnerability, an attacker can create a new folder under the Folder Redirection root path and create a junction on a newly created User folder. When the new user logs in, Folder Redirection would start redirecting to the folder and copying personal data.

This elevation of privilege vulnerability can only be addressed by reconfiguring Folder Redirection with Offline files and restricting permissions, and NOT via a security update for affected Windows Servers. See the FAQ section of this CVE for configuration guidance.

Affected products named by the advisory: Windows Server 2008 R2 Service Pack 1; Windows Server 2008 R2 Service Pack 1 (Server Core installation); Windows Server 2008 Service Pack 2; Windows Server 2008 Service Pack 2 (Server Core installation); and 11 more.

Affected products named by the advisory: Windows Server 2012 (Server Core installation); Windows Server 2012 R2 (Server Core installation); Windows Server 2016 (Server Core installation); Windows Server 2019 (Server Core installation); and 3 more.