Microsoft released updates for the Meltdown and Spectre vulnerabilities in January for all supported versions of Windows, including Windows 7, and although further mitigations have been taken recently, it appears that the initial fix opened the door to a different kind of exploit.
Security researcher Ulf Frisk discovered that the Meltdown security patch for Windows 7 and Windows Server 2008 R2 allows normal processes to gain full read and write access to physical memory. This means that anyone who managed to exploit the flaw gained administrator privileges on vulnerable machines.
The flaw analysis technique and the proof-of-concept exploit published online reveal that exploiting the flaw was not a complicated process at all.
The bug, which was caused by the updated Meltdown code release of January for Windows 7 and Windows Server 2008 R2, was fixed by Microsoft in the March 2018 Patch Tuesday. This means that only computers that use the January and February patches are vulnerable, while those that have not installed new updates since December 2017 are safe. Modern machines where the security fixes of this month have already been applied are also protected.
All other Windows versions, including Windows 8.1 and Windows 10, are also secure, because the updated Meltdown code version did not cause the same vulnerability.
It is obvious that Windows 7 systems must deploy the latest patches to stay protected, especially if they run the January or February updates.
