Microsoft’s April 2021 Patch Tuesday, comes five zero-day vulnerabilities and more Critical Microsoft Exchange vulnerabilities.

Microsoft has fixed 108 vulnerabilities, with 19 classified as Critical and 89 as Important. Excluding Chromium Edge Vulnerability released earlier this month

There are also five zero-day vulnerabilities patched today that were publicly disclosed, with one known to be used in attacks. Microsoft fixed four critical Microsoft Exchange vulnerabilities that the NSA discovered.

Five zero-day vulnerabilities fixed

Microsoft has fixed four publicly disclosed vulnerabilities and one actively exploited vulnerability.

  • CVE-2021-27091– Remote Mapper Service Elevation of Privilege Vulnerability
  • CVE-2021-28412 – Windows NTFS Denial of Service Vulnerability
  • CVE-2021-28437 – Windows Installer Information Disclosure Vulnerability – PolarBear
  • CVE-2021-28458 – Azure ms-rest-node auth Library Elevation of Privilege Vulnerability

Exploited in wild

  • CVE-2021-28310 – Win32k Elevation of Privilege Vulnerability

CVE-2021-28310 exploited was utilized by the BITTER APT group, Privilege escalation escaping sandboxing

Microsoft Exchange vulnerabilities

Microsoft Exchange admins are not getting any rest as four more Critical remote code execution vulnerabilities discovered by the NSA were fixed in Microsoft Exchange today. Two of these vulnerabilities are pre-authentication, which means they do not require attackers to log in to the server first.

  • CVE-2021-28480 – Microsoft Exchange Server Remote Code Execution Vulnerability
  • CVE-2021-28481– Microsoft Exchange Server Remote Code Execution Vulnerability
  • CVE-2021-28482 – Microsoft Exchange Server Remote Code Execution Vulnerability
  • CVE-2021-28483 – Microsoft Exchange Server Remote Code Execution Vulnerability

On a Nutshell , This month update includes fixes for the products below

  • Azure AD Web Sign-in
  • Azure DevOps
  • Azure Sphere
  • Microsoft Edge (Chromium-based)
  • Microsoft Exchange Server
  • Microsoft Graphics Component
  • Microsoft Internet Messaging API
  • Microsoft NTFS
  • Microsoft Office Excel
  • Microsoft Office Outlook
  • Microsoft Office SharePoint
  • Microsoft Office Word
  • Microsoft Windows Codecs Library
  • Microsoft Windows Speech
  • Open Source Software
  • DNS Server
  • Hyper-V
  • Visual Studio
  • Visual Studio Code
  • Visual Studio Code – GitHub Pull Requests and Issues Extension
  • Visual Studio Code – Kubernetes Tools
  • Visual Studio Code – Maven for Java Extension
  • Windows Application Compatibility Cache
  • Windows AppX Deployment Extensions
  • Windows Console Driver
  • Windows Diagnostic Hub
  • Windows Early Launch Antimalware Driver
  • Windows ELAM
  • Windows Event Tracing
  • Windows Installer
  • Windows Kernel
  • Windows Media Player
  • Windows Network File System
  • Windows Overlay Filter
  • Windows Portmapping
  • Windows Registry
  • Windows Remote Procedure Call Runtime
  • Windows Resource Manager
  • Windows Secure Kernel Mode
  • Windows Services and Controller App
  • Windows SMB Server
  • Windows TCP/IP
  • Windows Win32K
  • Windows WLAN Auto Config Service.