Microsoft December 2021 Patch Tuesday fixes an actively exploited zero-day

Microsoft December 2021 Patch Tuesday addresses 67 vulnerabilities, including an actively exploited Windows Installer vulnerability.

Microsoft December 2021 Patch Tuesday addressed 67 vulnerabilities in Microsoft Windows and Windows Components, ASP.NET Core and Visual Studio, Azure Bot Framework SDK, Internet Storage Name Service, Defender for IoT, Edge (Chromium-based), Microsoft Office and Office Components, SharePoint Server, PowerShell, Remote Desktop Client, Windows Hyper-V, Windows Mobile Device Management, Windows Remote Access Connection Manager, TCP/IP, and the Windows Update Stack.

Below is the vulnerabilities addressed by Microsoft:

• 21 Elevation of Privilege Vulnerabilities
• 26 Remote Code Execution Vulnerabilities
• 10 Information Disclosure Vulnerabilities
• 3 Denial of Service Vulnerabilities
• 7 Spoofing Vulnerabilities

Seven of the issues addressed by Microsoft are rated as critical, while the remaining ones are rated as Important in severity. One of the vulnerabilities fixed by Microsoft, tracked as CVE-2021-43890, is under active exploitation.

“We have investigated reports of a spoofing vulnerability in AppX installer that affects Microsoft Windows. Microsoft is aware of attacks that attempt to exploit this vulnerability by using specially crafted packages that include the malware family known as Emotet/Trickbot/Bazaloader.” reads the advisory published by Microsoft.

An attacker could exploit the vulnerability by tricking the victims into opening a specially crafted attachment sent via phishing messages.

The other zero-day vulnerabilities addressed by the company as part of the December 2021 Patch Tuesday are:

• CVE-2021-43240 – NTFS Set Short Name Elevation of Privilege Vulnerability
• CVE-2021-41333 – Windows Print Spooler Elevation of Privilege Vulnerability
• CVE-2021-43880 – Windows Mobile Device Management Elevation of Privilege Vulnerability
• CVE-2021-43883 – Windows Installer Elevation of Privilege Vulnerability
• CVE-2021-43893 – Windows Encrypting File System (EFS) Elevation of Privilege Vulnerability

The full list of vulnerabilities addressed by Microsoft is available here:

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Pierluigi Paganini

(SecurityAffairs – hacking, Microsoft December 2021 Patch Tuesday)

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