Four zero-days vulnerabilities and 71 flaws fixed via this month’s Patch Tuesday

Alexandru Poloboc
by Alexandru Poloboc
News Editor
With an overpowering desire to always get to the bottom of things and uncover the truth, Alex spent most of his time working as a news reporter, anchor, as well as TV and radio... Read more
Affiliate Disclosure
  • Redmond officials addressed a lot of problems with this month's rollout, more than expected.
  • The Microsoft Word Remote Code Execution Vulnerability was treated as a critical one.
  • Also considered critical was the Windows Hyper-V Remote Code Execution Vulnerability.
  • This article contains the complete list of security updates that were issued in October 2021.
pt oct 2021

Today is Microsoft’s October 2021 Patch Tuesday, and with it comes fixes for four zero-day vulnerabilities and a total of 74 flaws.

Microsoft has fixed 74 vulnerabilities (81 including Microsoft Edge) with today’s update, with three classified as Critical, and 70 as Important, and one as Low.

4 zero-days vulnerabilities fixed, with one actively exploited

These 81 vulnerabilities that are being patched during this month’s rollout are split into categories, as follows:

  • 21 Elevation of Privilege Vulnerabilities
  • 6 Security Feature Bypass Vulnerabilities
  • 20 Remote Code Execution Vulnerabilities
  • 13 Information Disclosure Vulnerabilities
  • 5 Denial of Service Vulnerabilities
  • 9 Spoofing Vulnerabilities

October’s Patch Tuesday includes fixes for four zero-day vulnerabilities, with a Win32k Elevation of Privilege Vulnerability vulnerability known to have been actively exploited in attacks.

Microsoft classifies a vulnerability as a zero-day if it is publicly disclosed or actively exploited with no official fix available.

The actively exploited vulnerability was discovered by Kaspersky’s Boris Larin (oct0xor) and allows malware or a threat actor to gain elevated privileges on a Windows device.

Kaspersky disclosed that the vulnerability was used by threat actors in “widespread espionage campaigns against IT companies, military/defense contractors, and diplomatic entities.” 

As part of the attacks, the threat actors installed a remote access trojan (RAT) that was elevated with higher permissions using the zero-day Windows vulnerability. 

Thus, Kaspersky calls this cluster of malicious activity MysterSnail and is attributed to the IronHusky and Chinese-speaking APT activity.

Microsoft also fixed three other publicly disclosed vulnerabilities that are not known to be exploited in attacks.

  • CVE-2021-40469 – Windows DNS Server Remote Code Execution Vulnerability
  • CVE-2021-41335 – Windows Kernel Elevation of Privilege Vulnerability
  • CVE-2021-41338 – Windows AppContainer Firewall Rules Security Feature Bypass Vulnerability

Other companies also released important updates

  • Adobe’s October security updates were released for various applications.
  • Android’s October security updates were released last week.
  • Apache released HTTP Web Server 2.4.51 to fix an incompete patch for an actively exploited vulnerability.
  • Apple released security updates for iOS and iPadOS yesterday that an actively exploited zero-day vulnerability.
  • Cisco released security updates for numerous products this month.
  • SAP released its October 2021 security updates.
  • VMware released a security update for VMware vRealize Operations.

This month’s security updates

Below is the complete list of resolved vulnerabilities and released advisories in the October 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.

Tag CVE ID CVE Title Severity
.NET Core & Visual Studio CVE-2021-41355 .NET Core and Visual Studio Information Disclosure Vulnerability Important
Active Directory Federation Services CVE-2021-41361 Active Directory Federation Server Spoofing Vulnerability Important
Console Window Host CVE-2021-41346 Console Window Host Security Feature Bypass Vulnerability Important
HTTP.sys CVE-2021-26442 Windows HTTP.sys Elevation of Privilege Vulnerability Important
Microsoft DWM Core Library CVE-2021-41339 Microsoft DWM Core Library Elevation of Privilege Vulnerability Important
Microsoft Dynamics CVE-2021-40457 Microsoft Dynamics 365 Customer Engagement Cross-Site Scripting Vulnerability Important
Microsoft Dynamics CVE-2021-41353 Microsoft Dynamics 365 (on-premises) Spoofing Vulnerability Important
Microsoft Dynamics CVE-2021-41354 Microsoft Dynamics 365 (on-premises) Cross-site Scripting Vulnerability Important
Microsoft Edge (Chromium-based) CVE-2021-37978 Chromium: CVE-2021-37978 Heap buffer overflow in Blink Unknown
Microsoft Edge (Chromium-based) CVE-2021-37979 Chromium: CVE-2021-37979 Heap buffer overflow in WebRTC Unknown
Microsoft Edge (Chromium-based) CVE-2021-37980 Chromium: CVE-2021-37980 Inappropriate implementation in Sandbox Unknown
Microsoft Edge (Chromium-based) CVE-2021-37977 Chromium: CVE-2021-37977 Use after free in Garbage Collection Unknown
Microsoft Edge (Chromium-based) CVE-2021-37974 Chromium: CVE-2021-37974 Use after free in Safe Browsing Unknown
Microsoft Edge (Chromium-based) CVE-2021-37975 Chromium: CVE-2021-37975 Use after free in V8 Unknown
Microsoft Edge (Chromium-based) CVE-2021-37976 Chromium: CVE-2021-37976 Information leak in core Unknown
Microsoft Exchange Server CVE-2021-26427 Microsoft Exchange Server Remote Code Execution Vulnerability Important
Microsoft Exchange Server CVE-2021-34453 Microsoft Exchange Server Denial of Service Vulnerability Important
Microsoft Exchange Server CVE-2021-41348 Microsoft Exchange Server Elevation of Privilege Vulnerability Important
Microsoft Exchange Server CVE-2021-41350 Microsoft Exchange Server Spoofing Vulnerability Important
Microsoft Graphics Component CVE-2021-41340 Windows Graphics Component Remote Code Execution Vulnerability Important
Microsoft Intune CVE-2021-41363 Intune Management Extension Security Feature Bypass Vulnerability Important
Microsoft Office Excel CVE-2021-40473 Microsoft Excel Remote Code Execution Vulnerability Important
Microsoft Office Excel CVE-2021-40472 Microsoft Excel Information Disclosure Vulnerability Important
Microsoft Office Excel CVE-2021-40471 Microsoft Excel Remote Code Execution Vulnerability Important
Microsoft Office Excel CVE-2021-40474 Microsoft Excel Remote Code Execution Vulnerability Important
Microsoft Office Excel CVE-2021-40485 Microsoft Excel Remote Code Execution Vulnerability Important
Microsoft Office Excel CVE-2021-40479 Microsoft Excel Remote Code Execution Vulnerability Important
Microsoft Office SharePoint CVE-2021-40487 Microsoft SharePoint Server Remote Code Execution Vulnerability Important
Microsoft Office SharePoint CVE-2021-40483 Microsoft SharePoint Server Spoofing Vulnerability Low
Microsoft Office SharePoint CVE-2021-40484 Microsoft SharePoint Server Spoofing Vulnerability Important
Microsoft Office SharePoint CVE-2021-40482 Microsoft SharePoint Server Information Disclosure Vulnerability Important
Microsoft Office SharePoint CVE-2021-41344 Microsoft SharePoint Server Remote Code Execution Vulnerability Important
Microsoft Office Visio CVE-2021-40480 Microsoft Office Visio Remote Code Execution Vulnerability Important
Microsoft Office Visio CVE-2021-40481 Microsoft Office Visio Remote Code Execution Vulnerability Important
Microsoft Office Word CVE-2021-40486 Microsoft Word Remote Code Execution Vulnerability Critical
Microsoft Windows Codecs Library CVE-2021-40462 Windows Media Foundation Dolby Digital Atmos Decoders Remote Code Execution Vulnerability Important
Microsoft Windows Codecs Library CVE-2021-41330 Microsoft Windows Media Foundation Remote Code Execution Vulnerability Important
Microsoft Windows Codecs Library CVE-2021-41331 Windows Media Audio Decoder Remote Code Execution Vulnerability Important
Rich Text Edit Control CVE-2021-40454 Rich Text Edit Control Information Disclosure Vulnerability Important
Role: DNS Server CVE-2021-40469 Windows DNS Server Remote Code Execution Vulnerability Important
Role: Windows Active Directory Server CVE-2021-41337 Active Directory Security Feature Bypass Vulnerability Important
Role: Windows AD FS Server CVE-2021-40456 Windows AD FS Security Feature Bypass Vulnerability Important
Role: Windows Hyper-V CVE-2021-40461 Windows Hyper-V Remote Code Execution Vulnerability Critical
Role: Windows Hyper-V CVE-2021-38672 Windows Hyper-V Remote Code Execution Vulnerability Critical
System Center CVE-2021-41352 SCOM Information Disclosure Vulnerability Important
Visual Studio CVE-2020-1971 OpenSSL: CVE-2020-1971 EDIPARTYNAME NULL pointer de-reference Important
Visual Studio CVE-2021-3450 OpenSSL: CVE-2021-3450 CA certificate check bypass with X509_V_FLAG_X509_STRICT Important
Visual Studio CVE-2021-3449 OpenSSL: CVE-2021-3449 NULL pointer deref in signature_algorithms processing Important
Windows AppContainer CVE-2021-41338 Windows AppContainer Firewall Rules Security Feature Bypass Vulnerability Important
Windows AppContainer CVE-2021-40476 Windows AppContainer Elevation Of Privilege Vulnerability Important
Windows AppX Deployment Service CVE-2021-41347 Windows AppX Deployment Service Elevation of Privilege Vulnerability Important
Windows Bind Filter Driver CVE-2021-40468 Windows Bind Filter Driver Information Disclosure Vulnerability Important
Windows Cloud Files Mini Filter Driver CVE-2021-40475 Windows Cloud Files Mini Filter Driver Information Disclosure Vulnerability Important
Windows Common Log File System Driver CVE-2021-40443 Windows Common Log File System Driver Elevation of Privilege Vulnerability Important
Windows Common Log File System Driver CVE-2021-40467 Windows Common Log File System Driver Elevation of Privilege Vulnerability Important
Windows Common Log File System Driver CVE-2021-40466 Windows Common Log File System Driver Elevation of Privilege Vulnerability Important
Windows Desktop Bridge CVE-2021-41334 Windows Desktop Bridge Elevation of Privilege Vulnerability Important
Windows DirectX CVE-2021-40470 DirectX Graphics Kernel Elevation of Privilege Vulnerability Important
Windows Event Tracing CVE-2021-40477 Windows Event Tracing Elevation of Privilege Vulnerability Important
Windows exFAT File System CVE-2021-38663 Windows exFAT File System Information Disclosure Vulnerability Important
Windows Fastfat Driver CVE-2021-41343 Windows Fast FAT File System Driver Information Disclosure Vulnerability Important
Windows Fastfat Driver CVE-2021-38662 Windows Fast FAT File System Driver Information Disclosure Vulnerability Important
Windows Installer CVE-2021-40455 Windows Installer Spoofing Vulnerability Important
Windows Kernel CVE-2021-41336 Windows Kernel Information Disclosure Vulnerability Important
Windows Kernel CVE-2021-41335 Windows Kernel Elevation of Privilege Vulnerability Important
Windows MSHTML Platform CVE-2021-41342 Windows MSHTML Platform Remote Code Execution Vulnerability Important
Windows Nearby Sharing CVE-2021-40464 Windows Nearby Sharing Elevation of Privilege Vulnerability Important
Windows Network Address Translation (NAT) CVE-2021-40463 Windows NAT Denial of Service Vulnerability Important
Windows Print Spooler Components CVE-2021-41332 Windows Print Spooler Information Disclosure Vulnerability Important
Windows Print Spooler Components CVE-2021-36970 Windows Print Spooler Spoofing Vulnerability Important
Windows Remote Procedure Call Runtime CVE-2021-40460 Windows Remote Procedure Call Runtime Security Feature Bypass Vulnerability Important
Windows Storage Spaces Controller CVE-2021-40489 Storage Spaces Controller Elevation of Privilege Vulnerability Important
Windows Storage Spaces Controller CVE-2021-41345 Storage Spaces Controller Elevation of Privilege Vulnerability Important
Windows Storage Spaces Controller CVE-2021-26441 Storage Spaces Controller Elevation of Privilege Vulnerability Important
Windows Storage Spaces Controller CVE-2021-40478 Storage Spaces Controller Elevation of Privilege Vulnerability Important
Windows Storage Spaces Controller CVE-2021-40488 Storage Spaces Controller Elevation of Privilege Vulnerability Important
Windows TCP/IP CVE-2021-36953 Windows TCP/IP Denial of Service Vulnerability Important
Windows Text Shaping CVE-2021-40465 Windows Text Shaping Remote Code Execution Vulnerability Important
Windows Win32K CVE-2021-40449 Win32k Elevation of Privilege Vulnerability Important
Windows Win32K CVE-2021-41357 Win32k Elevation of Privilege Vulnerability Important
Windows Win32K CVE-2021-40450 Win32k Elevation of Privilege Vulnerability Important

Have you been struggling with any of the errors and bugs listed in this article? Let us know in the comments section below.

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