CVE-2021-38646

What this means for your business

• It affects Microsoft Office. It matters if your company, or a supplier that handles your data, runs it.
• Attackers are already using it. CISA added it to its list of flaws used in real attacks on 28 March 2022.
• Ransomware gangs are known to have used it.
• An attacker can use it only with access to the machine itself, without a login, but only after tricking someone into an action such as opening a file or a link.
• FIRST's prediction model gives it a 8% chance of attack attempts being seen in the next 30 days, ranking above 94% of all known flaws.

What to do

1. 1Check whether your company or your suppliers run Microsoft Office, and which version. The affected versions are listed further down this page.
2. 2If you do, apply the vendor's fix. A patch or vendor advisory has been published.
3. 3Treat it as urgent. US federal agencies must fix it by 18 April 2022. That deadline does not apply to private companies, but it shows how seriously CISA takes it.
4. 4Because attackers have used it, check the affected systems for signs of a break-in, not only for the update.