patch tuesday

Microsoft formally released fixes for 112 newly discovered security vulnerabilities as part of its November 2020 Patch Tuesday, including an actively exploited zero-day flaw disclosed by Google's security team last week.

The rollout addresses flaws, 17 of which are rated as Critical, 93 are rated as Important, and two are rated Low in severity, once again bringing the patch count over 110 after a drop last month.

The security updates encompass a range of software, including Microsoft Windows, Office and Office Services and Web Apps, Internet Explorer, Edge, ChakraCore, Exchange Server, Microsoft Dynamics, Windows Codecs Library, Azure Sphere, Windows Defender, Microsoft Teams, and Visual Studio.


Chief among those fixed is CVE-2020-17087 (CVSS score 7.8), a buffer overflow flaw in Windows Kernel Cryptography Driver ("cng.sys") that was disclosed on October 30 by the Google Project Zero team as being used in conjunction with a Chrome zero-day to compromise Windows 7 and Windows 10 users.

For its part, Google released an update for its Chrome browser to address the zero-day (CVE-2020-15999) last month.

Microsoft's advisory about the flaw doesn't go into any details beyond the fact that it was a "Windows Kernel Local Elevation of Privilege Vulnerability" in part to restructure security advisories in line with the Common Vulnerability Scoring System (CVSS) format starting this month.

Outside of the zero-day, the update fixes a number of remote code execution (RCE) vulnerabilities impacting Exchange Server (CVE-2020-17084), Network File System (CVE-2020-17051), and Microsoft Teams (CVE-2020-17091), as well as a security bypass flaw in Windows Hyper-V virtualization software (CVE-2020-17040).

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CVE-2020-17051 is rated 9.8 out of a maximum 10 on the CVSS score, making it a critical vulnerability. Microsoft, however, noted that the attack complexity of the flaw — the conditions beyond the attacker's control that must exist in order to exploit the vulnerability — is low.

As with the zero-day, the advisories associated with these security shortcomings are light on descriptions, with little to no information on how these RCE flaws are abused or which security feature in Hyper-V is being bypassed.

Other critical flaws fixed by Microsoft this month include memory corruption vulnerabilities in Microsoft Scripting Engine (CVE-2020-17052) and Internet Explorer (CVE-2020-17053), and multiple RCE flaws in HEVC Video Extensions Codecs library.

It's highly recommended that Windows users and system administrators apply the latest security patches to resolve the threats associated with these issues.

To install the latest security updates, Windows users can head to Start > Settings > Update & Security > Windows Update, or by selecting Check for Windows updates.

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