Microsoft Internet Explorer: memory corruption flaw under attack

What is affected

Microsoft Internet Explorer is found on ordinary personal computers and phones, so this is not only a problem for companies. If you use it and have not updated since the fix was released, you are exposed.

A use-after-free vulnerability exists within CDisplayPointer in Microsoft Internet Explorer that allows an attacker to remotely execute arbitrary code.

What an attacker can do

This is a memory corruption flaw. It lets an attacker corrupt the program's memory by feeding it specially crafted content: a web page, a file or a network message. The result ranges from a crash to the attacker running their own code.

How it is reached

Over the internet or network

Access the attacker needs

No account needed

Does the victim have to do something?

Yes, the victim must open or click something

What to do

1. Update Microsoft Internet Explorer now. Open the update or "About" screen, install whatever is offered and restart the app or device, because the fix is not active until you do.
2. Turn on automatic updates so the next fix arrives without you having to look for it.
3. If your device is too old to receive this update, stop using the affected app for anything sensitive and plan a replacement.

Apply updates per vendor instructions.

How urgent is it

CISA added this vulnerability to its Known Exploited Vulnerabilities catalogue on March 3, 2022, which means there is reliable evidence of attacks in the wild. US federal agencies must fix it by March 24, 2022, a deadline that has already passed. That deadline does not bind anyone else, but it shows how seriously the agency rates it.

The EPSS model estimates a 77% probability that this flaw will be exploited somewhere in the next 30 days. That is higher than 99.5% of all scored vulnerabilities.

Its CVSS severity score is 8.8 out of 10 (high), as recorded in the US National Vulnerability Database.

Technical description

Use-after-free vulnerability in the CDisplayPointer class in mshtml.dll in Microsoft Internet Explorer 6 through 11 allows remote attackers to execute arbitrary code or cause a denial of service (memory corruption) via crafted JavaScript code that uses the onpropertychange event handler, as exploited in the wild in September and October 2013, aka "Internet Explorer Memory Corruption Vulnerability."