Advisory Details

March 15th, 2021

Microsoft Windows User Profile Service Directory Junction Privilege Escalation Vulnerability

ZDI-21-283
ZDI-CAN-12194

CVE ID CVE-2021-26873
CVSS SCORE 7.0, (AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H)
AFFECTED VENDORS Microsoft
AFFECTED PRODUCTS Windows
VULNERABILITY DETAILS

This vulnerability allows local attackers to escalate privileges on affected installations of Microsoft Windows. An attacker must first obtain the ability to execute low-privileged code on the target system in order to exploit this vulnerability.

The specific flaw exists within the User Profile Service. By creating a directory junction, an attacker can abuse the service to create a second junction in a sensitive location. An attacker can leverage this vulnerability to escalate privileges and execute arbitrary code in the context of SYSTEM.

ADDITIONAL DETAILS Microsoft has issued an update to correct this vulnerability. More details can be found at:
https://msrc.microsoft.com/update-guide/vulnerability/CVE-2021-26873
DISCLOSURE TIMELINE
  • 2020-11-11 - Vulnerability reported to vendor
  • 2021-03-15 - Coordinated public release of advisory
CREDIT Abdelhamid Naceri (halov)
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