Microsoft has released important “Patch Tuesday” monthly security updates. These should applied promptly as some of these vulnerabilities have potential to be actively exploited in-the-wild later:

This month we got patches for 50 vulnerabilities. Of these, 5 are critical, 2 were previously disclosed and 6 is already being exploited according to Microsoft.

The highlight this time, of course, goes to the 6 zero-days: an elevation of privileges vulnerability on Microsoft DWM Core Library (CVE-2021-33739) – the only previously disclosed, an elevation of privilege vulnerability on Windows NTFS (CVE-2021-31956), an information disclosure vulnerability on Windows Kernel (CVE-2021-31955), an elevation of privilege vulnerability on Microsoft Enhanced Cryptographic Provider (CVE-2021-31201 and CVE-2021-31199) and, more importaltly, a remote code execution vulnerability affecting Windows MSHTML Platform (CVE-2021-33742).

Apart from the zero-days, there is an important security feature bypass Vulnerability Kerberos AppContainer (CVE-2021-31962). According to the advisory, in an enterprise environment this vulnerability might allow an attacker to bypass Kerberos authentication, to authenticate to an arbitrary service principal name. This vulnerability was associated to the highest CVSS this month: 9.4.