Google has discovered a vulnerability in Microsoft Windows. It is a local privilege escalation in the Windows win32k.sys kernel driver that can be used as a security sandbox escape. The vulnerability is a NULL pointer dereference in win32k!MNGetpItemFromIndexwhen NtUserMNDragOver() system call is called under specific circumstances.
We strongly believe this vulnerability may only be exploitable on Windows 7 due to recent exploit mitigations added in newer versions of Windows. To date, we have only observed active exploitation against Windows 7 32-bit systems.
Pursuant to Google’s vulnerability disclosure policy, when they discovered the vulnerability it was reported to Microsoft. Today, also in compliance with the policy, Google are publicly disclosing its existence, because it is a serious vulnerability in Windows that we know was being actively exploited in targeted attacks. The unpatched Windows vulnerability can still be used to elevate privileges or combined with another browser vulnerability to evade security sandboxes. Microsoft have told us they are working on a fix.
As mitigation advice for this vulnerability users should consider upgrading to Windows 10 if they are still running an older version of Windows, and to apply Windows patches from Microsoft when they become available. We will update this post when they are available.
Microsoft has not yet given a date for when its patch for Windows 7 will be released, but said it would be “as soon as possible”.
Duncan is a technology professional with over 20 years experience of working in various IT roles. He has a interest in cyber security, and has a wide range of other skills in radio, electronics and telecommunications.