Advisory Details

July 19th, 2021

(Pwn2Own) Microsoft Windows win32kfull Bitmap Use-After-Free Privilege Escalation Vulnerability

ZDI-21-825
ZDI-CAN-13580

CVE ID CVE-2021-34498
CVSS SCORE 8.8, AV:L/AC:L/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 handling of bitmap objects. The issue results from the lack of validating the existence of an object prior to performing operations on the object. 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-2021-34498
DISCLOSURE TIMELINE
  • 2021-04-27 - Vulnerability reported to vendor
  • 2021-07-19 - Coordinated public release of advisory
CREDIT Marcin Wiazowski
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