Microsoft April 2021 Patch Tuesday Fixes 108 Flaws, 5 Zero-days

Today is Microsoft’s April 2021 Patch Tuesday, and with it comes five zero-day vulnerabilities and more Critical Microsoft Exchange vulnerabilities. It has been a tough couple of months for Windows and Microsoft Exchange admins, and it looks like April won’t be any easier, so please be nice to your IT staff today.

With today’s update, Microsoft has fixed 108 vulnerabilities, with 19 classified as Critical and 89 as Important. These numbers do not include the 6 Chromium Edge vulnerabilities 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.

To make matters worse, Microsoft fixed four critical Microsoft Exchange vulnerabilities that the NSA discovered.

For information about the non-security Windows updates, you can read about today’s Windows 10 KB5001330 & KB5001337 cumulative updates.

Five zero-day vulnerabilities fixed

As part of today’s Patch Tuesday, Microsoft has fixed four publicly disclosed vulnerabilities and one actively exploited vulnerability.

The following four vulnerabilities Microsoft states were publicly exposed but not exploited:

• CVE-2021-27091 – RPC Endpoint Mapper Service Elevation of Privilege Vulnerability
• CVE-2021-28312 – Windows NTFS Denial of Service Vulnerability
• CVE-2021-28437 – Windows Installer Information Disclosure Vulnerability – PolarBear
• CVE-2021-28458 – Azure ms-rest-nodeauth Library Elevation of Privilege Vulnerability

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The following vulnerability discovered by Kaspersky researcher Boris Larin was found exploited in the wild.

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

Kaspersky believes the CVE-2021-28310 exploited was utilized by the BITTER APT group.

“We believe this exploit is used in the wild, potentially by several threat actors. It is an escalation of privilege (EoP) exploit that is likely used together with other browser exploits to escape sandboxes or get system privileges for further access. “

“Unfortunately, we weren’t able to capture a full chain, so we don’t know if the exploit is used with another browser zero-day, or coupled with known, patched vulnerabilities,” Kaspersky explained in new blog post.

NSA discovers 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.

None of these vulnerabilities are known to have been actively exploited and are tracked with the following CVEs:

• 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

Admins can find more information about these vulnerabilities here.

Recent updates from other companies

Other vendors who released updates in April include:

• Adobereleased security updates for Adobe Creative Cloud Desktop, Framemaker, and Connect.
• Android’s April security updates were released last week.
• Apple released GarageBand securty updates but has not provided details as to what has been fixed.
• Cisco released security updates for numerous products this month.
• SAP released its April 2021 security updates.

The April 2021 Patch Tuesday Security Updates

Below is the full list of resolved vulnerabilities and released advisories in the April 2021 Patch Tuesday updates. To access the full description of each vulnerability and the systems that it affects, you can view the full report here.

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Tag	CVE ID	CVE Title	Severity
Azure AD Web Sign-in	CVE-2021-27092	Azure AD Web Sign-in Security Feature Bypass Vulnerability	Important
Azure DevOps	CVE-2021-28459	Azure DevOps Server Spoofing Vulnerability	Important
Azure DevOps	CVE-2021-27067	Azure DevOps Server and Team Foundation Server Information Disclosure Vulnerability	Important
Azure Sphere	CVE-2021-28460	Azure Sphere Unsigned Code Execution Vulnerability	Critical
Microsoft Edge (Chromium-based)	CVE-2021-21199	Chromium: CVE-2021-21199 Use Use after free in Aura	Unknown
Microsoft Edge (Chromium-based)	CVE-2021-21194	Chromium: CVE-2021-21194 Use after free in screen capture	Unknown
Microsoft Edge (Chromium-based)	CVE-2021-21197	Chromium: CVE-2021-21197 Heap buffer overflow in TabStrip	Unknown
Microsoft Edge (Chromium-based)	CVE-2021-21198	Chromium: CVE-2021-21198 Out of bounds read in IPC	Unknown
Microsoft Edge (Chromium-based)	CVE-2021-21195	Chromium: CVE-2021-21195 Use after free in V8	Unknown
Microsoft Edge (Chromium-based)	CVE-2021-21196	Chromium: CVE-2021-21196 Heap buffer overflow in TabStrip	Unknown
Microsoft Exchange Server	CVE-2021-28480	Microsoft Exchange Server Remote Code Execution Vulnerability	Critical
Microsoft Exchange Server	CVE-2021-28482	Microsoft Exchange Server Remote Code Execution Vulnerability	Critical
Microsoft Exchange Server	CVE-2021-28483	Microsoft Exchange Server Remote Code Execution Vulnerability	Critical
Microsoft Exchange Server	CVE-2021-28481	Microsoft Exchange Server Remote Code Execution Vulnerability	Critical
Microsoft Graphics Component	CVE-2021-28350	Windows GDI+ Remote Code Execution Vulnerability	Important
Microsoft Graphics Component	CVE-2021-28318	Windows GDI+ Information Disclosure Vulnerability	Important
Microsoft Graphics Component	CVE-2021-28348	Windows GDI+ Remote Code Execution Vulnerability	Important
Microsoft Graphics Component	CVE-2021-28349	Windows GDI+ Remote Code Execution Vulnerability	Important
Microsoft Internet Messaging API	CVE-2021-27089	Microsoft Internet Messaging API Remote Code Execution Vulnerability	Important
Microsoft NTFS	CVE-2021-28312	Windows NTFS Denial of Service Vulnerability	Moderate
Microsoft NTFS	CVE-2021-27096	NTFS Elevation of Privilege Vulnerability	Important
Microsoft Office Excel	CVE-2021-28456	Microsoft Excel Information Disclosure Vulnerability	Important
Microsoft Office Excel	CVE-2021-28451	Microsoft Excel Remote Code Execution Vulnerability	Important
Microsoft Office Excel	CVE-2021-28454	Microsoft Excel Remote Code Execution Vulnerability	Important
Microsoft Office Excel	CVE-2021-28449	Microsoft Office Remote Code Execution Vulnerability	Important
Microsoft Office Outlook	CVE-2021-28452	Microsoft Outlook Memory Corruption Vulnerability	Important
Microsoft Office SharePoint	CVE-2021-28450	Microsoft SharePoint Denial of Service Update	Important
Microsoft Office Word	CVE-2021-28453	Microsoft Word Remote Code Execution Vulnerability	Important
Microsoft Windows Codecs Library	CVE-2021-28464	VP9 Video Extensions Remote Code Execution Vulnerability	Important
Microsoft Windows Codecs Library	CVE-2021-28466	Raw Image Extension Remote Code Execution Vulnerability	Important
Microsoft Windows Codecs Library	CVE-2021-27079	Windows Media Photo Codec Information Disclosure Vulnerability	Important
Microsoft Windows Codecs Library	CVE-2021-28468	Raw Image Extension Remote Code Execution Vulnerability	Important
Microsoft Windows Codecs Library	CVE-2021-28317	Microsoft Windows Codecs Library Information Disclosure Vulnerability	Important
Microsoft Windows DNS	CVE-2021-28323	Windows DNS Information Disclosure Vulnerability	Important
Microsoft Windows DNS	CVE-2021-28328	Windows DNS Information Disclosure Vulnerability	Important
Microsoft Windows Speech	CVE-2021-28351	Windows Speech Runtime Elevation of Privilege Vulnerability	Important
Microsoft Windows Speech	CVE-2021-28436	Windows Speech Runtime Elevation of Privilege Vulnerability	Important
Microsoft Windows Speech	CVE-2021-28347	Windows Speech Runtime Elevation of Privilege Vulnerability	Important
Open Source Software	CVE-2021-28458	Azure ms-rest-nodeauth Library Elevation of Privilege Vulnerability	Important
Role: Hyper-V	CVE-2021-28441	Windows Hyper-V Information Disclosure Vulnerability	Important
Role: Hyper-V	CVE-2021-28314	Windows Hyper-V Elevation of Privilege Vulnerability	Important
Role: Hyper-V	CVE-2021-28444	Windows Hyper-V Security Feature Bypass Vulnerability	Important
Role: Hyper-V	CVE-2021-26416	Windows Hyper-V Denial of Service Vulnerability	Important
Visual Studio	CVE-2021-27064	Visual Studio Installer Elevation of Privilege Vulnerability	Important
Visual Studio Code	CVE-2021-28457	Visual Studio Code Remote Code Execution Vulnerability	Important
Visual Studio Code	CVE-2021-28471	Remote Development Extension for Visual Studio Code Remote Code Execution Vulnerability	Important
Visual Studio Code	CVE-2021-28475	Visual Studio Code Remote Code Execution Vulnerability	Important
Visual Studio Code	CVE-2021-28473	Visual Studio Code Remote Code Execution Vulnerability	Important
Visual Studio Code	CVE-2021-28477	Visual Studio Code Remote Code Execution Vulnerability	Important
Visual Studio Code	CVE-2021-28469	Visual Studio Code Remote Code Execution Vulnerability	Important
Visual Studio Code – GitHub Pull Requests and Issues Extension	CVE-2021-28470	Visual Studio Code GitHub Pull Requests and Issues Extension Remote Code Execution Vulnerability	Important
Visual Studio Code – Kubernetes Tools	CVE-2021-28448	Visual Studio Code Kubernetes Tools Remote Code Execution Vulnerability	Important
Visual Studio Code – Maven for Java Extension	CVE-2021-28472	Visual Studio Code Maven for Java Extension Remote Code Execution Vulnerability	Important
Windows Application Compatibility Cache	CVE-2021-28311	Windows Application Compatibility Cache Denial of Service Vulnerability	Important
Windows AppX Deployment Extensions	CVE-2021-28326	Windows AppX Deployment Server Denial of Service Vulnerability	Important
Windows Console Driver	CVE-2021-28438	Windows Console Driver Denial of Service Vulnerability	Important
Windows Console Driver	CVE-2021-28443	Windows Console Driver Denial of Service Vulnerability	Important
Windows Diagnostic Hub	CVE-2021-28313	Diagnostics Hub Standard Collector Service Elevation of Privilege Vulnerability	Important
Windows Diagnostic Hub	CVE-2021-28321	Diagnostics Hub Standard Collector Service Elevation of Privilege Vulnerability	Important
Windows Diagnostic Hub	CVE-2021-28322	Diagnostics Hub Standard Collector Service Elevation of Privilege Vulnerability	Important
Windows Early Launch Antimalware Driver	CVE-2021-28447	Windows Early Launch Antimalware Driver Security Feature Bypass Vulnerability	Important
Windows ELAM	CVE-2021-27094	Windows Early Launch Antimalware Driver Security Feature Bypass Vulnerability	Important
Windows Event Tracing	CVE-2021-27088	Windows Event Tracing Elevation of Privilege Vulnerability	Important
Windows Event Tracing	CVE-2021-28435	Windows Event Tracing Information Disclosure Vulnerability	Important
Windows Installer	CVE-2021-26413	Windows Installer Spoofing Vulnerability	Important
Windows Installer	CVE-2021-28440	Windows Installer Elevation of Privilege Vulnerability	Important
Windows Installer	CVE-2021-28437	Windows Installer Information Disclosure Vulnerability	Important
Windows Installer	CVE-2021-26415	Windows Installer Elevation of Privilege Vulnerability	Important
Windows Kernel	CVE-2021-27093	Windows Kernel Information Disclosure Vulnerability	Important
Windows Kernel	CVE-2021-28309	Windows Kernel Information Disclosure Vulnerability	Important
Windows Media Player	CVE-2021-28315	Windows Media Video Decoder Remote Code Execution Vulnerability	Critical
Windows Media Player	CVE-2021-27095	Windows Media Video Decoder Remote Code Execution Vulnerability	Critical
Windows Network File System	CVE-2021-28445	Windows Network File System Remote Code Execution Vulnerability	Important
Windows Overlay Filter	CVE-2021-26417	Windows Overlay Filter Information Disclosure Vulnerability	Important
Windows Portmapping	CVE-2021-28446	Windows Portmapping Information Disclosure Vulnerability	Important
Windows Registry	CVE-2021-27091	RPC Endpoint Mapper Service Elevation of Privilege Vulnerability	Important
Windows Remote Procedure Call Runtime	CVE-2021-28336	Remote Procedure Call Runtime Remote Code Execution Vulnerability	Critical
Windows Remote Procedure Call Runtime	CVE-2021-28335	Remote Procedure Call Runtime Remote Code Execution Vulnerability	Critical
Windows Remote Procedure Call Runtime	CVE-2021-28334	Remote Procedure Call Runtime Remote Code Execution Vulnerability	Critical
Windows Remote Procedure Call Runtime	CVE-2021-28338	Remote Procedure Call Runtime Remote Code Execution Vulnerability	Critical
Windows Remote Procedure Call Runtime	CVE-2021-28434	Remote Procedure Call Runtime Remote Code Execution Vulnerability	Important
Windows Remote Procedure Call Runtime	CVE-2021-28337	Remote Procedure Call Runtime Remote Code Execution Vulnerability	Critical
Windows Remote Procedure Call Runtime	CVE-2021-28333	Remote Procedure Call Runtime Remote Code Execution Vulnerability	Critical
Windows Remote Procedure Call Runtime	CVE-2021-28327	Remote Procedure Call Runtime Remote Code Execution Vulnerability	Important
Windows Remote Procedure Call Runtime	CVE-2021-28329	Remote Procedure Call Runtime Remote Code Execution Vulnerability	Critical
Windows Remote Procedure Call Runtime	CVE-2021-28330	Remote Procedure Call Runtime Remote Code Execution Vulnerability	Critical
Windows Remote Procedure Call Runtime	CVE-2021-28332	Remote Procedure Call Runtime Remote Code Execution Vulnerability	Critical
Windows Remote Procedure Call Runtime	CVE-2021-28331	Remote Procedure Call Runtime Remote Code Execution Vulnerability	Critical
Windows Remote Procedure Call Runtime	CVE-2021-28354	Remote Procedure Call Runtime Remote Code Execution Vulnerability	Important
Windows Remote Procedure Call Runtime	CVE-2021-28339	Remote Procedure Call Runtime Remote Code Execution Vulnerability	Critical
Windows Remote Procedure Call Runtime	CVE-2021-28355	Remote Procedure Call Runtime Remote Code Execution Vulnerability	Important
Windows Remote Procedure Call Runtime	CVE-2021-28353	Remote Procedure Call Runtime Remote Code Execution Vulnerability	Important
Windows Remote Procedure Call Runtime	CVE-2021-28352	Remote Procedure Call Runtime Remote Code Execution Vulnerability	Important
Windows Remote Procedure Call Runtime	CVE-2021-28357	Remote Procedure Call Runtime Remote Code Execution Vulnerability	Important
Windows Remote Procedure Call Runtime	CVE-2021-28358	Remote Procedure Call Runtime Remote Code Execution Vulnerability	Important
Windows Remote Procedure Call Runtime	CVE-2021-28356	Remote Procedure Call Runtime Remote Code Execution Vulnerability	Important
Windows Remote Procedure Call Runtime	CVE-2021-28346	Remote Procedure Call Runtime Remote Code Execution Vulnerability	Important
Windows Remote Procedure Call Runtime	CVE-2021-28342	Remote Procedure Call Runtime Remote Code Execution Vulnerability	Important
Windows Remote Procedure Call Runtime	CVE-2021-28340	Remote Procedure Call Runtime Remote Code Execution Vulnerability	Important
Windows Remote Procedure Call Runtime	CVE-2021-28341	Remote Procedure Call Runtime Remote Code Execution Vulnerability	Important
Windows Remote Procedure Call Runtime	CVE-2021-28345	Remote Procedure Call Runtime Remote Code Execution Vulnerability	Important
Windows Remote Procedure Call Runtime	CVE-2021-28344	Remote Procedure Call Runtime Remote Code Execution Vulnerability	Important
Windows Remote Procedure Call Runtime	CVE-2021-28343	Remote Procedure Call Runtime Remote Code Execution Vulnerability	Critical
Windows Resource Manager	CVE-2021-28320	Windows Resource Manager PSM Service Extension Elevation of Privilege Vulnerability	Important
Windows Secure Kernel Mode	CVE-2021-27090	Windows Secure Kernel Mode Elevation of Privilege Vulnerability	Important
Windows Services and Controller App	CVE-2021-27086	Windows Services and Controller App Elevation of Privilege Vulnerability	Important
Windows SMB Server	CVE-2021-28325	Windows SMB Information Disclosure Vulnerability	Important
Windows SMB Server	CVE-2021-28324	Windows SMB Information Disclosure Vulnerability	Important
Windows TCP/IP	CVE-2021-28439	Windows TCP/IP Driver Denial of Service Vulnerability	Important
Windows TCP/IP	CVE-2021-28442	Windows TCP/IP Information Disclosure Vulnerability	Important
Windows TCP/IP	CVE-2021-28319	Windows TCP/IP Driver Denial of Service Vulnerability	Important
Windows Win32K	CVE-2021-27072	Win32k Elevation of Privilege Vulnerability	Important
Windows Win32K	CVE-2021-28310	Win32k Elevation of Privilege Vulnerability	Important
Windows WLAN Auto Config Service	CVE-2021-28316	Windows WLAN AutoConfig Service Security Feature Bypass Vulnerability	Important