This week Microsoft released its security updates for April 2021, which has fixes for 108 vulnerabilities in Microsoft products. Every month we will post our vulnerability risk and tips around each patch released, to provide advice for IT professionals and businesses.

Out of the 108 patches; 19 are classed as critical and 89 are classed as important. These do not include the 6 Chromium Edge vulnerabilities released earlier this month. There were also 5 Zero-Days and more Critical Microsoft Exchange Vulnerabilities discovered this month:

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

  • CVE-2021-27091 - RPC Endpoint Mapper Service Elevation of Privilege Vulnerability. 

  • CVE-2021-28312 - Windows NTFS Denial of Service Vulnerability.

  • CVE-2021-28458 - Azure ms-rest-nodeauth Library Elevation of Privilege Vulnerability.

  • CVE-2021-28437 - Windows Installer Information Disclosure Vulnerability - PolarBear.

Microsoft also released fixes for 4 Microsoft Exchange vulnerabilities not exploited in attacks:

  • 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

Other Products:

Other companies who have released security updates this week:

- Adobe: released security updates for Adobe Creative Cloud Desktop, FrameMaker &          Connect.

- Android: April security updates were released last week.

- Apple: released GarageBand security updates but has not provided details as to what      has been fixed.

- Cisco: released security updates for numerous products.

- SAP: released it’s April 2021 security updates.

 

All the patches can be found in the table below or alternatively downloaded here.

We have also curated a downloadable Patching Best Practice Guide.

 

Category

CVE IDs

CVE Title 

Severity

FIT Score & Tip

Azure AD Web Sign-In
1

CVE-2021-27092

Azure AD Web Sign-in Security Feature Bypass Vulnerability

Important

4/5 - This is an update for more modern OS (Windows 10 / Server 2019) which relates to a security vulnerability. It's worth patching this as it well. It forms part of the cumulative update for April 2021.

Azure DevOps 2

CVE-2021-28459 CVE-2021-27067

Azure DevOps Server Spoofing Vulnerability

Azure DevOps Server and Team Foundation Server Information Disclosure Vulnerability

Important

3/5 - If you use Azure DevOps Server, this is a separate patch that can be downloaded directly and applied.

Azure Sphere   1

CVE-2021-28460

Azure Sphere Unsigned Code Execution Vulnerability

Critical

4/5 - As labelled Critical, pay this particular attention. This is a command-based update run directly on your Azure Sphere devices.

Microsoft Edge (Chromium-based)

6

CVE-2021-21199 CVE-2021-21194 CVE-2021-21197 CVE-2021-21198 CVE-2021-21195

Chromium: CVE-2021-21199 Use Use after free in Aura

Chromium: CVE-2021-21194 Use after free in screen capture

Chromium: CVE-2021-21197 Heap buffer overflow in TabStrip

Chromium: CVE-2021-21198 Out of bounds read in IPC

Chromium: CVE-2021-21195 Use after free in V8

Chromium: CVE-2021-21196 Heap buffer overflow in TabStrip

Unknown

3/5 - This really depends on if your users utilise Microsoft Edge, If they don't use it - still patch it. As it's possible it has been left on the machine and could be accessed or used, thus allowing accessibility in via these CVEs.

Microsoft Exchange Server

4

CVE-2021-28480 CVE-2021-28482 CVE-2021-28483 CVE-2021-28481

Microsoft Exchange Server Remote Code Execution Vulnerability

Critical

4/5 - After last months Exchange vulnerabilities, It would be worth continuing the trend this month and ensuring that Exchange is up to date.

Microsoft Graphics Component

4

CVE-2021-28350 CVE-2021-28318 CVE-2021-28348 CVE-2021-28349

Windows GDI+ Remote Code Execution Vulnerability

Windows GDI+ Information Disclosure Vulnerability

Important

3/5 - This forms part of monthly updates for Server O/S and also in monthly cumulative updates.

Microsoft Internet Messaging API - 1

CVE-2021-27089

Microsoft Internet Messaging API Remote Code Execution Vulnerability

Important

3/5 - This forms part of monthly updates for Server O/S and also in monthly cumulative updates.

Microsoft NTFS

2

CVE-2021-28312 CVE-2021-27096

Windows NTFS Denial of Service Vulnerability

NTFS Elevation of Privilege Vulnerability

Important

4/5 - NTFS is the file system version for Windows, and with elevation of privilege this could compromise security. One to update when possible.

Microsoft Office Excel

4

CVE-2021-28456 CVE-2021-28451 CVE-2021-28454 CVE-2021-28449

Microsoft Excel Information Disclosure Vulnerability

Microsoft Excel Remote Code Execution Vulnerability

Microsoft Excel Remote Code Execution Vulnerability

Microsoft Office Remote Code Execution Vulnerability

Important

4/5 - Most, if not all users, will often use the Office suite, so it's recommended to update these as soon as possible. The main reason is your weakest vector is your end-users.

Microsoft Office Outlook

1

CVE-2021-28452

Microsoft Outlook Memory Corruption Vulnerability

Important

4/5 - Most, if not all users, will often use the Office suite, so it's recommended to update these as soon as possible. The main reason is your weakest vector is your end-users.

Microsoft Office SharePoint

1

CVE-2021-28450

Microsoft SharePoint Denial of Service Update

Important

4/5 - Most, if not all users, will often use the Office suite, so it's recommended to update these as soon as possible. The main reason is your weakest vector is your end-users.

Microsoft Office Word

1

CVE-2021-28453

Microsoft Word Remote Code Execution Vulnerability

Important

4/5 - Most, if not all users, will often use the Office suite, so it's recommended to update these as soon as possible. The main reason is your weakest vector is your end-users.

Microsoft Windows Codecs Library

5

CVE-2021-28464 CVE-2021-28466 CVE-2021-27079 CVE-2021-28468 CVE-2021-28317

VP9 Video Extensions Remote Code Execution Vulnerability

Raw Image Extension Remote Code Execution Vulnerability

Windows Media Photo Codec Information Disclosure Vulnerability

Raw Image Extension Remote Code Execution Vulnerability

Microsoft Windows Codecs Library Information Disclosure Vulnerability

Important

3/5 - It's worth reading into this one, as some of the updates come from the Microsoft Store (or Microsoft Store for Business).

Microsoft Windows DNS

2

CVE-2021-28323 CVE-2021-28328

Windows DNS Information Disclosure Vulnerability

Important

3/5 - Most Windows networks will utilise Windows based DNS. I'd recommend updating this when possible. Once again this forms part of the monthly updates which are released.

Microsoft Windows Speech
3

CVE-2021-28351 CVE-2021-28436 CVE-2021-28347 

Windows Speech Runtime Elevation of Privilege Vulnerability

Important

3/5 - This vulnerability is resolved within your normal routine monthly updates. 

Open Source Software
1

CVE-2021-28458

Azure ms-rest-nodeauth Library Elevation of Privilege Vulnerability

Important

3/5 - This vulnerability is resolved within your normal routine monthly updates.

Role: Hyper-V
4

CVE-2021-28441
CVE-2021-28314
CVE-2021-28444
CVE-2021-26416

Windows Hyper-V Information Disclosure Vulnerability
Windows Hyper-V Elevation of Privilege Vulnerability
Windows Hyper-V Security Feature Bypass Vulnerability
Windows Hyper-V Denial of Service Vulnerability

Important

4/5 - Hyper-V is a pivotal part of any infrastructure (of course, only if you use it). Once again, this is in monthly patching, so applying the monthly updates should resolve this. Some of these are only applicable to later operating systems (Windows 10 / Server 2019 onwards)

Visual Studio
1

CVE-2021-27064

Visual Studio Installer Elevation of Privilege Vulnerability

Important

2/5 - Worth applying if you use Visual Studio, but worth noting this vulnerability is for the installer only. 

Visual Studio Code
6

CVE-2021-28457
CVE-2021-28471
CVE-2021-28475
CVE-2021-28475
CVE-2021-28477
CVE-2021-28469 

Visual Studio Code Remote Code Execution Vulnerability
Remote Development Extension for Visual Studio Code Remote Code Execution Vulnerability

Important

2/5 - Visual Studio Code is open source and this can be freely downloaded from the link that the CVE references. 

Visual Studio Code - GitHub Pull Requests and Issues Extension
1

CVE-2021-28470

Visual Studio Code GitHub Pull Requests and Issues Extension Remote Code Execution Vulnerability

Important

2/5 - This is applicable if you use the reference extension only. You can download this from the CVE which is reference.

Visual Studio Code - Kubernetes Tools
1

CVE-2021-28448 

Visual Studio Code Kubernetes Tools Remote Code Execution Vulnerability

Important

2/5 - This is applicable if you use the reference extension only. You can download this from the CVE which is reference. 

Visual Studio Code - Maven for Java Extension
1

CVE-2021-28472 

Visual Studio Code Maven for Java Extension Remote Code Execution Vulnerability

Important

2/5 - This is applicable if you use the reference extension only. You can download this from the CVE which is reference.

Windows Application Compatibility Cache
1

CVE-2021-28311 

Windows Application Compatibility Cache Denial of Service Vulnerability

Important

3/5 - This vulnerability is resolved within your normal routine monthly updates. 

Windows AppX Deployment Extensions
1

CVE-2021-28326

Windows AppX Deployment Server Denial of Service Vulnerability

Important

3/5 - This vulnerability is resolved within your normal routine monthly updates. 

Windows Console Driver
2

CVE-2021-28438
CVE-2021-28443

Windows Console Driver Denial of Service Vulnerability

Important

3/5 - This vulnerability is resolved within your normal routine monthly updates.

Windows Diagnostic Hub
3

CVE-2021-28313
CVE-2021-28321
CVE-2021-28322

Diagnostics Hub Standard Collector Service Elevation of Privilege Vulnerability

Important

3/5 - This vulnerability is resolved within your normal routine monthly updates.

Windows Early Launch Antimalware Driver
1

CVE-2021-28447

Windows Early Launch Antimalware Driver Security Feature Bypass Vulnerability

Important

3/5 - This vulnerability is resolved within your normal routine monthly updates.

Windows ELAM
1

CVE-2021-27094

Windows Early Launch Antimalware Driver Security Feature Bypass Vulnerability

Important

3/5 - This vulnerability is resolved within your normal routine monthly updates.

Windows Event Tracing
2

CVE-2021-27088
CVE-2021-28435

Windows Event Tracing Elevation of Privilege Vulnerability

Important

3/5 - This vulnerability is resolved within your normal routine monthly updates.

Windows Installer
4

CVE-2021-26413
CVE-2021-28440
CVE-2021-24837
CVE-2021-26415

Windows Installer Spoofing Vulnerability
Windows Installer Elevation of Privilege Vulnerability
Windows Installer Information Disclosure Vulnerability

Important

4/5 - Windows Installer is used for installing programs and also doing Windows Update. It's used more often than not, and utilised by the operating system in the background too. I'd recommend getting your monthly updates done when you can to resolve this.

Windows Kernel
2

CVE-2021-27093
CVE-2021-28309

Windows Kernel Information Disclosure Vulnerability

Important

4/5 - The Windows Kernel is the heart and brain of the OS, a bit like other operating systems - the Kernel is the core component of the functional operating system. This forms part of the monthly updates.

Windows Media Player
2

CVE-2021-28315
CVE-2021-27095

Windows Media Video Decoder Remote Code Execution Vulnerability

Critical

4/5 - Flagged as Critical by Microsoft, these fixes are within your monthly updates for April 2021.

Windows Network File System
1

CVE-2021-28445

Windows Network File System Remote Code Execution Vulnerability

Important

3/5 - This vulnerability is resolved within your normal routine monthly updates.

Windows Overlay Filter
1

CVE-2021-26417

Windows Overlay Filter Information Disclosure Vulnerability

Important

3/5 - This is for more modern operating systems (Windows 10 and later server operating systems) but once again included within your monthly patches.

Windows Portmapping
1

CVE-2021-28446

Windows Portmapping Information Disclosure Vulnerability

Important

3/5 - This vulnerability is resolved within your normal routine monthly updates.

Windows Registry
1

CVE-2021-27091

RPC Endpoint Mapper Service Elevation of Privilege Vulnerability

Important

3/5 - There are some specific operating systems in the CVSS, so worth a review to see if this effects you. It tends to be older operating systems but does relate to Registry - which is important.

Windows Remote Procedure Call Runtime
12

CVE-2021-28336
CVE-2021-28335
CVE-2021-28334
CVE-2021-28338
CVE-2021-28337
CVE-2021-28333
CVE-2021-28329
CVE-2021-28330
CVE-2021-28332
CVE-2021-28331
CVE-2021-28339
CVE-2021-28343

Remote Procedure Call Runtime Remote Code Execution Vulnerability

Critical

4/5 - Although flagged as exploitation less likely, these CVE's require network access and a low privilege account, which would be why the critical severity has been assigned. This is once again in the monthly rollout of patchings and available in cumulative or monthly updates for April 2021

Windows Remote Procedure Call Runtime
15

CVE-2021-28434
CVE-2021-28327
CVE-2021-28354
CVE-2021-28355
CVE-2021-28353
CVE-2021-28352
CVE-2021-28357
CVE-2021-28358
CVE-2021-28356
CVE-2021-28346
CVE-2021-28342
CVE-2021-28340
CVE-2021-28341
CVE-2021-28345
CVE-2021-28344

Remote Procedure Call Runtime Remote Code Execution Vulnerability

Important

4/5 - These complement the patches mentioned above, they all resolve parts of the same issues stated above, however these are flagged as important rather than critical and once again found in the April 2021 patches.

Windows Resource Manager
1

CVE-2021-28320

Windows Resource Manager PSM Service Extension Elevation of Privilege Vulnerability

Important

3/5 - Applicable to later operating systems (Windows 10 and later versions of Server - 2016 onwards) Once again, this is in your monthly patches for April 2021.

Windows Secure Kernel Mode
1

CVE-2021-27090

Windows Secure Kernel Mode Elevation of Privilege Vulnerability

Important

3/5 - The exploitation is known to be easy. Local access is required to approach this attack. A simple authentication is needed for exploitation.

Windows Services and Controller App
1

CVE-2021-27086

Windows Services and Controller App Elevation of Privilege Vulnerability

Important

3/5 - The exploitation is known to be easy. Local access is required to approach this attack. A simple authentication is needed for exploitation.

Windows SMB Server
2

CVE-2021-28325
CVE-2021-28324

Windows SMB Information Disclosure Vulnerability

Important

2/5 - This issue affects an unknown code block of the component SMB. The manipulation with an unknown input leads to an information disclosure vulnerability

Windows TCP/IP
3

CVE-2021-28439
CVE-2021-28442
CVE-2021-28319

Windows TCP/IP Information Disclosure Vulnerability
Windows TCP/IP Driver Denial of Service Vulnerability

Important

3/5 - Affected by this issue is an unknown functionality of the component TCP/IP Driver. The manipulation with an unknown input leads to a denial of service vulnerability.

Windows Win32K
2

CVE-2021-27072
CVE-2021-28310

Win32k Elevation of Privilege Vulnerability

Important

3/5 - The exploitability is told to be difficult. Local access is required to approach this attack. The successful exploitation needs an authentication. The technical details are unknown and an exploit is not available.

Windows WLAN Auto Config Service
1

CVE-2021-28316

Windows WLAN AutoConfig Service Security Feature Bypass Vulnerability

Important

3/5 - Difficult to exploit. The manipulation with an unknown input leads to an information disclosure vulnerability via the WLAN AutoConfig Service.

 

Hope this table with helpful! 

Lizzie Arcari

Lizzie joined Foundation IT in 2019 after graduating from University. She is excited to start her career in the IT industry, learning from the best.