Exchange Server zero-day among latest Microsoft Patch Tuesday fixes

The firm has patched three zero-day vulnerabilities across its products that haven’t yet been exploited

The Microsoft Exchange Server software being accessed on a notebook device

Microsoft has patched 55 vulnerabilities across a swathe of its products as part of its latest round of Patch Tuesday fixes, including three zero-day vulnerabilities that haven’t yet been publicly exploited.

The most alarming of the flaws, tracked as CVE-2021-31207, is present in the Microsoft Exchange Server platform, which was at the heart of a devastating supply chain attack earlier in the year. 

This vulnerability is a security feature bypass flaw and was discovered as part of last month’s Pwn2Own contest. Although it hasn’t been exploited by cyber criminals, details of the exploitation demonstrated in the contest will be published soon.

The Exchange Server flaw has been patched alongside CVE-2021-31204, an elevation of privilege vulnerability in .NET and Visual Studio, as well as CVE-2021-31200, a remote code execution flaw in the Common Utilities component.  

Four of the flaws patched as part of the 55 are classed as ‘critical’, and none of them are the three zero-days highlighted. These include remote code execution flaws in HTTP.sys, Windows OLE Automation and Hyper-V, as well as a scripting engine memory corruption bug in Internet Explorer.

The 55 CVEs patched in May represents the smallest wave of Patch Tuesday fixes so far in 2021, after more than 100 were addressed this time last month. This wave included patches for five zero-days vulnerabilities and four critical Microsoft Exchange Server flaws discovered by the NSA. 

Related Resource

The definitive guide to IT security

Protecting your MSP and your customers

The definitive guide to IT security for MSPs - whitepaper from LiongardDownload now

The most serious of the five zero-days included CVE-2021-28310, an escalation of privilege flaw in the Desktop Window Manager component of Windows 10 that was likely being used in a chain alongside other vulnerabilities to seize control of machines.

Although CVE-2021-31207, patched this month, is deemed as less likely to be exploited, cyber criminals will be working hard to reverse engineer an exploit from the fix released this week.

The fact that details around a successful exploitation, as demonstrated in the Pwn2Own contest, could be published soon too, should urge businesses to patch their vulnerable systems as soon as possible.

Featured Resources

How to choose an AI vendor

Five key things to look for in an AI vendor

Download now

The UK 2020 Databerg report

Cloud adoption trends in the UK and recommendations for cloud migration

Download now

2021 state of email security report: Ransomware on the rise

Securing the enterprise in the COVID world

Download now

The impact of AWS in the UK

How AWS is powering Britain's fastest-growing companies

Download now

Recommended

ProtectedBy.AI’s CodeLock blocks malware at source code level
software as a service (SaaS)

ProtectedBy.AI’s CodeLock blocks malware at source code level

9 Jun 2021
CISOs aren’t leading by example when it comes to cyber security
cyber security

CISOs aren’t leading by example when it comes to cyber security

24 May 2021
New report highlights the need for diversity in cyber security recruitment
cyber security

New report highlights the need for diversity in cyber security recruitment

28 Apr 2021
FCC commissioner calls for big tech to help bridge digital divide
digital divide

FCC commissioner calls for big tech to help bridge digital divide

2 Jun 2021

Most Popular

GitHub to prohibit code that’s used in active attacks
cyber security

GitHub to prohibit code that’s used in active attacks

7 Jun 2021
WWDC 2021: Apple unveils iOS 15, macOS Monterey and more
iOS

WWDC 2021: Apple unveils iOS 15, macOS Monterey and more

8 Jun 2021
OnePlus 9 Pro review: An instant cult classic
Hardware

OnePlus 9 Pro review: An instant cult classic

7 Jun 2021