December 2021 Patch Tuesday: Fixes for 67 vulnerabilities, including 6 zero-days

The last Patch Tuesday of this year is here, and it comes with fixes for 67 vulnerabilities, out of which seven are classified as Critical and 60 as Important. Six zero-day vulnerabilities have also been patched, one of which is being actively exploited. Needless to say, IT admins are going to have their hands full with this month’s patching and update process. 

After an initial discussion about the updates released, we’ll offer our advice for devising a plan to handle patch management in a hybrid work environment. You can also register for our free Patch Tuesday webinar and listen to our experts break down the Patch Tuesday updates in detail. 

What is Patch Tuesday?

Patch Tuesday falls on the second Tuesday of every month. It is on this day that Microsoft releases security and non-security updates for its operating system and other related applications. Since Microsoft has upheld this process of releasing updates in a periodic manner, IT admins expect these updates and have time to gear up for them.

Why is Patch Tuesday important?

The most important security updates and patches to fix critical bugs or vulnerabilities are released on Patch Tuesday. Usually zero-day vulnerabilities are also fixed during Patch Tuesday unless the vulnerability is critical and highly exploited, in which case an out-of-band security update is released to address that particular vulnerability. 

December Patch Tuesday product lineup

Security updates were released for the following products: 

• ASP.NET Core & Visual Studio

• Microsoft Edge (Chromium-based)

• Microsoft Office

• Microsoft PowerShell

• Microsoft Windows Codecs Library

• Remote Desktop Client

• Role: Windows Hyper-V

• Visual Studio Code

• Windows Installer

• Windows Encrypting file system

• Windows Kernel

• Windows Media

• Windows NTFS

• Windows Print Spooler Components

• Windows Mobile Device Management

6 zero-day vulnerabilities patched

Of the six zero-day vulnerabilities patched this month, one is being actively exploited and the others are publicly disclosed but not actively exploited. Here is the list:

• CVE-2021-43890 – Windows AppX Installer Spoofing Vulnerability, which is being used in various malware distribution campaigns, including Emotet, TrickBot, and BazarLoader (actively exploited)

• CVE-2021-43240 – NTFS Set Short Name Elevation of Privilege Vulnerability  (publicly disclosed but not actively exploited)

• CVE-2021-41333 – Windows Print Spooler Elevation of Privilege Vulnerability (publicly disclosed but not actively exploited)

• CVE-2021-43880 – Windows Mobile Device Management Elevation of Privilege Vulnerability (publicly disclosed but not actively exploited)

• CVE-2021-43883 – Windows Installer Elevation of Privilege Vulnerability (publicly disclosed but not actively exploited)

• CVE-2021-43893 – Windows Encrypting File System (EFS) Elevation of Privilege Vulnerability (publicly disclosed but not actively exploited)

Critical updates

There are seven Critical updates released this Patch Tuesday: 

Third-party updates released after last month’s Patch Tuesday 

Third-party vendors such as Android, Cisco, Apple, SAP, and VMware have released updates after last month’s Patch Tuesday. Several security advisories for Apache Log4j have also been released in the past week.

Best practices to handle patch management in a hybrid work environment

Most organizations have opted to embrace remote work even after they have been cleared to return to the office. This decision poses various challenges to IT admins, especially in terms of managing and securing distributed endpoints. 

Here are a few pointers to simplify the process of remote patching. 

• Disable automatic updates because one faulty patch could bring down the whole system. IT admins can educate end users on how to disable automatic updates on their machines. Patch Manager Plus and Desktop Central also have a dedicated patch, 105427, that can be deployed to endpoints to ensure that automatic updates are disabled.

• Create a restore point—a backup or image that captures the state of the machines—before deploying big updates like those from Patch Tuesday.

• Establish a patching schedule and keep end users informed about it. It is recommended to set up a time for deploying patches and rebooting systems. Let end users know what needs to be done on their end for trouble-free patching.

• Test the patches on a pilot group of systems before deploying them to the production environment. This will ensure that the patches do not interfere with the workings of other applications.

• Since many users are working from home, they all might be working different hours; in this case, you can allow end users to skip deployment and scheduled reboots. This will give them the liberty to install updates at their convenience and avoid disrupting their work. Our patch management products come with options for user-defined deployment and reboot.

• Most organizations are patching using a VPN. To stop patch tasks from eating up your VPN bandwidth, install Critical patches and security updates first. You might want to hold off on deploying feature packs and cumulative updates since they are bulky updates and consume too much bandwidth.

• Schedule the non-security updates and security updates that are not rated Critical to be deployed after Patch Tuesday, such as during the third or fourth week of the month. You can also choose to decline certain updates if you feel they are not required in your environment.

• Run patch reports to get a detailed view of the health status of your endpoints.

• For machines belonging to users returning to the office after working remotely, check if they are compliant with your security policies. If not, quarantine them.

• Install the latest updates and feature packs before deeming your back-to-office machines fit for production.

• Take inventory of and remove apps that are now obsolete for your back-to-office machines, like remote collaboration software.

With Desktop Central or Patch Manager Plus, you can completely automate the entire process of patch management, from testing patches to deploying them. You can also tailor patch tasks according to your current situation. For a hands-on experience with either of these products, start a free, 30-day trial and keep thousands of applications patched and secure.

Want to learn more about Patch Tuesday updates? Join our experts as they break down this month’s Patch Tuesday updates and offer in-depth analysis. You can also ask our experts questions and have them answered right away. Register for our free Patch Tuesday webinar.

Happy patching!