Advisory Details

May 13th, 2021

Microsoft Windows WalletService Directory Junction Privilege Escalation Vulnerability

ZDI-21-571
ZDI-CAN-12792

CVE ID CVE-2021-31187
CVSS SCORE 7.8, AV:L/AC:L/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 WalletService. By creating a directory junction, an attacker can abuse the service to create a file in an arbitrary location. An attacker can leverage this vulnerability to escalate privileges and execute 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-2021-31187
DISCLOSURE TIMELINE
  • 2021-01-29 - Vulnerability reported to vendor
  • 2021-05-13 - Coordinated public release of advisory
CREDIT JeongOh Kyea (@kkokkokye) of THEORI
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