Microsoft Word: code execution flaw under attack

What is affected

Microsoft Word 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.

Microsoft Word allows attackers to execute remote code or cause a denial-of-service (DoS) via crafted RTF data.

What an attacker can do

This is a code execution flaw. It lets an attacker run their own commands or programs on the affected system. In practice that usually means taking it over: installing malware, stealing data or using it to reach other devices on the same network.

How it is reached

Needs access to the device or a file opened on it

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 Word 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 28, 2022, which means there is reliable evidence of attacks in the wild. US federal agencies must fix it by April 18, 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 53% probability that this flaw will be exploited somewhere in the next 30 days. That is higher than 99% of all scored vulnerabilities.

Its CVSS severity score is 7.8 out of 10 (high), as recorded in the US National Vulnerability Database.

Technical description

Microsoft Word 2003 SP3, 2007 SP2 and SP3, and 2010 SP1; Word Viewer; Office Compatibility Pack SP2 and SP3; and Office Web Apps 2010 SP1 allow remote attackers to execute arbitrary code or cause a denial of service (memory corruption) via crafted RTF data, aka "Word RTF 'listoverridecount' Remote Code Execution Vulnerability."