Use-after-free in Windows and Windows Server - CVE-2021-40449

Vulnerability identifier: #VU57249

CSH Severity: High

CVSS v4.0: CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:A/U:Amber

CVE-ID: CVE-2021-40449

CWE-ID: CWE-416

Exploitation vector: Local access

Exploit availability: The vulnerability is being exploited in the wild

Vendor: Microsoft

Affected software:
Windows
Windows Server

The vulnerability allows a local user to escalate privileges on the system.

The vulnerability exists due to a boundary error within the Win32k NtGdiResetDC function in Microsoft Windows kernel. A local user can run a specially crafted program to trigger a use-after-free error, when the function ResetDC is executed a second time for the same handle during execution of its own callback, and execute arbitrary code with elevated privileges.

Note, the vulnerability is being actively exploited in the wild.

Install updates from vendor's website.

• https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-40449
• https://securelist.com/mysterysnail-attacks-with-windows-zero-day/104509/
• https://www.virustotal.com/gui/file/b7fb3623e31fb36fc3d3a4d99829e42910cad4da4fa7429a2d99a838e004366e