CVE-2021-26887

Microsoft Windows Folder Redirection Elevation of Privilege Vulnerability

CVE-2021-26887 is fixed in 2 products on 1 platform, first by KB5000840, released March 9, 2021. It is not reported as exploited. Patch Radar priority: High.

High
CVSS
7.8
Important
Exploitation
None reported
Exploitation Less Likely
CISA KEV
Not listed
Not in the Known Exploited Vulnerabilities catalog
EPSS
0.0107
64th percentile

<p>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.</p> <p>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.</p> <p>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 <strong>FAQ</strong> section of this CVE for configuration guidance.</p>

Where it's fixed

ProductFixed inFixReleased
Microsoft
Windows Server 2012 KB5000840 Mar 9, 2021
Windows Server 2012 KB5000847 Mar 9, 2021
Windows Server 2012 (Server Core installation) KB5000840 Mar 9, 2021
Windows Server 2012 (Server Core installation) KB5000847 Mar 9, 2021

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