Drupal core: vulnerability 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.

Improper sanitization in the extension file names is present in Drupal core.

What an attacker can do

This is a vulnerability flaw. It lets an attacker misuse the product in a way its maker did not intend. CISA lists it because attackers are confirmed to be using it against real systems.

How it is reached

Over the internet or network

Access the attacker needs

A basic user account

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 January 18, 2022, which means there is reliable evidence of attacks in the wild. US federal agencies must fix it by July 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 35% probability that this flaw will be exploited somewhere in the next 30 days. That is higher than 98% 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

Drupal core does not properly sanitize certain filenames on uploaded files, which can lead to files being interpreted as the incorrect extension and served as the wrong MIME type or executed as PHP for certain hosting configurations. This issue affects: Drupal Drupal Core 9.0 versions prior to 9.0.8, 8.9 versions prior to 8.9.9, 8.8 versions prior to 8.8.11, and 7 versions prior to 7.74.