Advisory Details

April 12th, 2021

Microsoft Windows win32kfull MulGradientFill Untrusted Pointer Dereference Privilege Escalation Vulnerability

ZDI-21-403
ZDI-CAN-12568

CVE ID CVE-2021-27077
CVSS SCORE 7.8, (AV:L/AC:H/PR:L/UI:N/S:C/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 win32kfull.sys driver. The issue results from the lack of proper validation of a user-supplied value prior to dereferencing it as a pointer. 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-2021-27077
DISCLOSURE TIMELINE
  • 2020-12-23 - Vulnerability reported to vendor
  • 2021-04-12 - Coordinated public release of advisory
CREDIT Marcin Wiazowski
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