Advisory Details

March 15th, 2021

Microsoft Windows Update Agent Directory Junction Denial-of-Service Vulnerability

ZDI-21-286
ZDI-CAN-12442

CVE ID CVE-2021-26866
CVSS SCORE 6.1, (AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:H)
AFFECTED VENDORS Microsoft
AFFECTED PRODUCTS Windows
VULNERABILITY DETAILS

This vulnerability allows local attackers to create a denial-of-service condition 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 Windows Update Agent. By creating a directory junction, an attacker can abuse Windows Update Agent to delete a directory. An attacker can leverage this vulnerability to create a denial-of-service condition on the 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-2021-26866
DISCLOSURE TIMELINE
  • 2020-12-04 - Vulnerability reported to vendor
  • 2021-03-15 - Coordinated public release of advisory
CREDIT Abdelhamid Naceri (halov)
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