Critical Patches Issued for Microsoft Products, May 11, 2021

ITS ADVISORY NUMBER: 
2021-066 - UPDATED
DATE(S) ISSUED: 
Tuesday, May 11, 2021
DATE UPDATED: 
Tuesday, August 24, 2021
SUBJECT: 
Critical Patches Issued for Microsoft Products, May 11, 2021
OVERVIEW: 

Multiple vulnerabilities have been discovered in Microsoft products, the most severe of which could allow for arbitrary code execution in the context of the logged on user. Depending on the privileges associated with the user, an attacker could then install programs; view, change, or delete data; or create new accounts with full user rights. Users whose accounts are configured to have fewer user rights on the system could be less impacted than those who operate with administrative user rights.

ORIGINAL THREAT INTELLIGENCE:
There are no reports of these vulnerabilities being exploited in the wild.

August 24 - UPDATED THREAT INTELLIGENCE:

According to open source research, the following CVEs are actively being exploited in the wild through the ProxyShell vulnerabilities:

  • CVE-2021-31207 (Post-Authentication Arbitrary File Write, May 2021)
  • CVE-2021-34473 (Pre-Authentication Path Confusion, July 2021)
  • CVE-2021-34523 (Exchange PowerShell Backend Elevation of Privilege, July 2021)
SYSTEMS AFFECTED: 

  • .NET Core & Visual Studio

  • HTTP.sys

  • Internet Explorer

  • Microsoft Accessibility Insights for Web

  • Microsoft Bluetooth Driver

  • Microsoft Dynamics Finance & Operations

  • Microsoft Exchange Server

  • Microsoft Graphics Component

  • Microsoft Office

  • Microsoft Office Access

  • Microsoft Office Excel

  • Microsoft Office SharePoint

  • Microsoft Office Word

  • Microsoft Windows Codecs Library

  • Microsoft Windows IrDA

  • Open Source Software

  • Role: Hyper-V

  • Skype for Business and Microsoft Lync

  • Visual Studio

  • Visual Studio Code

  • Windows Container Isolation FS Filter Driver

  • Windows Container Manager Service

  • Windows Cryptographic Services

  • Windows CSC Service

  • Windows Desktop Bridge

  • Windows OLE

  • Windows Projected File System FS Filter

  • Windows RDP Client

  • Windows SMB

  • Windows SSDP Service

  • Windows WalletService

  • Windows Wireless Networking

RISK:

Government:

Large and medium government entities: High
Small government entities: Medium
Business:
Large and medium business entities: High
Small business entities: Medium
Home Users: Low
 
DESCRIPTION: 

Multiple vulnerabilities have been discovered in Microsoft products, the most severe of which could allow for arbitrary code execution.

A full list of all vulnerabilities can be found at the links in the references section.

Successful exploitation of the most severe of these vulnerabilities could result in an attacker gaining the same privileges as the logged-on user. Depending on the privileges associated with the user, an attacker could then install programs; view, change, or delete data; or create new accounts with full user rights. Users whose accounts are configured to have fewer user rights on the system could be less impacted than those who operate with administrative user rights.

ACTIONS: 
  • After appropriate testing, immediately apply appropriate patches or appropriate mitigations provided by Microsoft to vulnerable systems.
  • Run all software as a non-privileged user (one without administrative rights) to diminish the effects of a successful attack.
  • Remind all users not to visit untrusted websites or follow links provided by unknown or untrusted sources.
  • Inform and educate users regarding threats posed by hypertext links contained in emails or attachments especially from untrusted sources.
  • Apply the Principle of Least Privilege to all systems and services.

August 24 - UPDATED ACTIONS:

  • We recommend you update to the latest Microsoft Exchange security patch, monitor for new indicators of compromise and stay up-to-date on new information as it is released.