Drupal Core: code execution flaw under attack

What is affected

Drupal Core is mostly run by companies, schools and public bodies, not on home computers. You are unlikely to have it yourself, but organisations that hold your data may. Breaches that start with flaws like this one are how personal data ends up leaked.

In Drupal Core, some field types do not properly sanitize data from non-form sources. This can lead to arbitrary PHP code execution in some cases.

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

Over the internet or network

Access the attacker needs

No account needed

Does the victim have to do something?

No, works without the victim doing anything

What to do

1. At home: nothing to install. Keep your own devices updated and use a different password for every service, so that a breach at one organisation does not open your other accounts.
2. If you administer Drupal Core at work: apply the vendor's fix or mitigation now and review logs for signs of compromise, because the flaw was being exploited before it was listed.
3. If the product is past its support date and no fix exists, take it off the internet or retire it.

Apply updates per vendor instructions.

How urgent is it

CISA added this vulnerability to its Known Exploited Vulnerabilities catalogue on March 25, 2022, which means there is reliable evidence of attacks in the wild. US federal agencies must fix it by April 15, 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 92% probability that this flaw will be exploited somewhere in the next 30 days. That is higher than 99.8% of all scored vulnerabilities.

Its CVSS severity score is 8.1 out of 10 (high), as recorded in the US National Vulnerability Database.

Technical description

Some field types do not properly sanitize data from non-form sources in Drupal 8.5.x before 8.5.11 and Drupal 8.6.x before 8.6.10. This can lead to arbitrary PHP code execution in some cases. A site is only affected by this if one of the following conditions is met: The site has the Drupal 8 core RESTful Web Services (rest) module enabled and allows PATCH or POST requests, or the site has another web services module enabled, like JSON:API in Drupal 8, or Services or RESTful Web Services in Drupal 7. (Note: The Drupal 7 Services module itself does not require an update at this time, but you should apply other contributed updates associated with this advisory if Services is in use.)