VERT Threat Alert: May 2021 Patch Tuesday Analysis

Today’s VERT Alert addresses Microsoft’s May 2021 Security Updates. VERT is actively working on coverage for these vulnerabilities and expects to ship ASPL-943 on Wednesday, May 12th.

In-The-Wild & Disclosed CVEs

CVE-2021-31204

Up first in the list this month, we have a vulnerability that impacts .NET and Visual Studio and could allow a successful attacker to elevate their permissions. We see patches for Microsoft Visual Studio 2019 for Windows and macOS as well as .NET 5.0 and .NET Core 3.1. Microsoft indicates that while this has been publicly disclosed, it has not been exploited in the wild. There are additional details regarding this vulnerability available on the dotnet github page.

Microsoft has rated this as Exploitation Less Likely on the latest software release on the Exploitability Index.

CVE-2021-31207

Once again, we have a Microsoft Exchange Server vulnerability in the patch round-up. This time, it is a security feature bypass and is one of the Exchange vulnerabilities that was found during PWN2OWN 2021.

Microsoft has rated this as Exploitation Less Likely on the latest software release on the Exploitability Index.

CVE-2021-31200

This code execution vulnerability is found in Neural Network Intelligence (NNI), an open-source tool for managing AutoML experiments. Since it is an open-source project, you can see the code change that was made to resolve this vulnerability.  It is interesting to note that the fixed code was committed on Dec 21, 2020, but it did not make a Patch Tuesday release until May.

Microsoft has rated this as Exploitation Less Likely on the latest software release on the Exploitability Index.

CVE Breakdown by Tag

While historical Microsoft Security Bulletin groupings are gone, Microsoft vulnerabilities are tagged with an identifier. This list provides a breakdown of the CVEs on a per tag basis.

Tag CVE Count CVEs
.NET Core & Visual Studio 1 CVE-2021-31204
Windows WalletService 1 CVE-2021-31187
Microsoft Windows IrDA 1 CVE-2021-31184
Microsoft Office Word 1 CVE-2021-31180
Windows Container Isolation FS Filter Driver 1 CVE-2021-31190
HTTP.sys 1 CVE-2021-31166
Visual Studio 1 CVE-2021-27068
Windows SSDP Service 1 CVE-2021-31193
Internet Explorer 1 CVE-2021-26419
Microsoft Bluetooth Driver 1 CVE-2021-31182
Microsoft Windows Codecs Library 2 CVE-2021-31192, CVE-2021-28465
Jet Red and Access Connectivity 1 CVE-2021-28455
Open Source Software 1 CVE-2021-31200
Microsoft Office Excel 5 CVE-2021-31174, CVE-2021-31175, CVE-2021-31177, CVE-2021-31178, CVE-2021-31179
Skype for Business and Microsoft Lync 2 CVE-2021-26421, CVE-2021-26422
Microsoft Graphics Component 2 CVE-2021-31170, CVE-2021-31188
Microsoft Office SharePoint 7 CVE-2021-31171, CVE-2021-31172, CVE-2021-31173, CVE-2021-31181, CVE-2021-28474, CVE-2021-28478, CVE-2021-26418
Role: Hyper-V 1 CVE-2021-28476
Windows CSC Service 1 CVE-2021-28479
Microsoft Office 1 CVE-2021-31176
Windows Desktop Bridge 1 CVE-2021-31185
Microsoft Accessibility Insights for Web 1 CVE-2021-31936
Windows OLE 1 CVE-2021-31194
Visual Studio Code 3 CVE-2021-31211, CVE-2021-31213, CVE-2021-31214
Windows Wireless Networking 3 CVE-2020-24588, CVE-2020-24587, CVE-2020-26144
Microsoft Exchange Server 4 CVE-2021-31195, CVE-2021-31198, CVE-2021-31207, CVE-2021-31209
Microsoft Dynamics Finance & Operations 1 CVE-2021-28461
Windows Container Manager Service 5 CVE-2021-31165, CVE-2021-31167, CVE-2021-31168, CVE-2021-31169, CVE-2021-31208
Windows RDP Client 1 CVE-2021-31186
Windows Projected File System FS Filter 1 CVE-2021-31191
Windows SMB 1 CVE-2021-31205

Other Information

There were no advisories included in the May Security Guidance, but there was a vulnerability of note:

CVE-2021-31166

This is a code execution vulnerability in the HTTP Protocol stack of HTTP.sys that was discovered internally at Microsoft. It is important to note that this affects the most recent releases of Windows – Windows 10 2004 and 20H2 and Windows Server 2004 and 20H2. The biggest take-away from this vulnerability is that Microsoft has labeled it as wormable. For this reason, it should be patched ASAP.

Microsoft has rated this as Exploitation More Likely on the latest software release on the Exploitability Index.