Microsoft patches Internet Explorer zero-day under active attack

The latest wave of Patch Tuesday fixes also included several updates to address the Print Spooler component in Windows

Microsoft has issued a fix for an actively exploited zero-day vulnerability embedded in the browser engine that powers legacy Internet Explorer as part of its latest wave of Patch Tuesday updates.

Users are being urged to apply the patch for the vulnerability tracked as CVE-2021-40444, which has been exploited in limited, targeted attacks prior to being disclosed last week.

This flaw, rated 8.8 out of ten on the CVSS threat severity scale, is a remote code execution flaw embedded in the MSHTML browser engine that powers Internet Explorer. It allows hackers to craft a malicious ActiveX control to be used by a Microsoft Office document that hosts the browser engine, which they then trick victims into opening. 

Researchers with EXPMON and Mandiant first detected the vulnerability before reporting this to Microsoft, with the former labelling the exploit as “a highly sophisticated zero-day attack”. They added that the exploit uses “logical flaws” so abusing the vulnerability is perfectly reliable and dangerous. 

This vulnerability has been fixed alongside 66 bugs in core Microsoft products and 20 flaws in the Chromium-based Edge browser as part of September’s Patch Tuesday round of fixes. The products affected this month include Azure, Office, SharePoint Server, Windows, Windows DNS and the Windows Subsystem for Linux. 

Related Resource

Challenging the rules of security

Protecting data and simplifying IT management with Chrome OS

Whitepaper front coverFree download

Of the vulnerabilities highlighted in this month’s round of updates is yet more fixes for flaws in the Print Spooler component, which gave Windows users and IT admins several headaches earlier in the year. 

The latest flaws - tracked as CVE-2021-38671, CVE-2021-38667 and CVE-2021-40447 - are all elevation of privilege flaws and haven’t been exploited in the wild, unlike many previous Print Spooler vulnerabilities. They have, however, all been assigned a rating of 7.8 out of ten on the CVSS threat severity scale.

They’ve also come alongside an update for the remote code execution flaw in Print Spooler tracked as CVE-2021-36958, which was first disclosed on 11 August. This vulnerability was first discovered in December 2020, and allows an attacker to run arbitrary code on targeted machines with system-level privileges. This then lets them install programmes as well as view and edit data. Microsoft said last month that a functional exploit code was available, but that there were no signs it was being abused.

This round of Patch Tuesday updates dwarfs the 44 fixes released in August, although Microsoft generally tends to patch far more in any given month. For instance, the July wave of updates, for example, included patches for 117 separate vulnerabilities in Microsoft products.

Featured Resources

The definitive guide to warehouse efficiency

Get your free guide to creating efficiencies in the warehouse

Free download

The total economic impact™ of Datto

Cost savings and business benefits of using Datto Integrated Solutions

Download now

Three-step guide to modern customer experience

Support the critical role CX plays in your business

Free download

Ransomware report

The global state of the channel

Download now

Recommended

Bug fixes and app updates arrive with latest Windows 11 preview build
Microsoft Windows

Bug fixes and app updates arrive with latest Windows 11 preview build

17 Sep 2021
Podcast transcript: Are foldable phones more than a fad?
Mobile

Podcast transcript: Are foldable phones more than a fad?

17 Sep 2021
The IT Pro Podcast: Are foldable phones more than a fad?
Mobile

The IT Pro Podcast: Are foldable phones more than a fad?

17 Sep 2021
Microsoft appoints Brad Smith as vice chair
Careers & training

Microsoft appoints Brad Smith as vice chair

15 Sep 2021

Most Popular

What are the pros and cons of AI?
machine learning

What are the pros and cons of AI?

8 Sep 2021
Google takes down map showing homes of 111,000 Guntrader customers
data breaches

Google takes down map showing homes of 111,000 Guntrader customers

2 Sep 2021
Intuit plans end-to-end SMB platform after $12 billion Mailchimp acquisition
mergers and acquisitions

Intuit plans end-to-end SMB platform after $12 billion Mailchimp acquisition

14 Sep 2021