Fortinet FortiOS: file access flaw under attack

What is affected

Fortinet FortiOS 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.

Fortinet FortiOS contains a path traversal vulnerability that may allow a local privileged attacker to read and write files via crafted CLI commands.

What an attacker can do

This is a file access flaw. It lets an attacker read or write files they should never reach, such as configuration files that hold passwords, or upload a malicious file that the system then runs.

How it is reached

Needs access to the device or a file opened on it

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 Fortinet FortiOS 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.

Vendor advisories and fixes

• fortiguard.comwww.fortiguard.com/psirt/FG-IR-22-369

How urgent is it

CISA added this vulnerability to its Known Exploited Vulnerabilities catalogue on March 14, 2023, which means there is reliable evidence of attacks in the wild. US federal agencies must fix it by April 4, 2023, 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 11% probability that this flaw will be exploited somewhere in the next 30 days. That is higher than 96% of all scored vulnerabilities.

Its CVSS severity score is 7.1 out of 10 (high), as recorded in the US National Vulnerability Database.

Technical description

A improper limitation of a pathname to a restricted directory vulnerability ('path traversal') [CWE-22] in Fortinet FortiOS version 7.2.0 through 7.2.3, 7.0.0 through 7.0.9 and before 6.4.11 allows a privileged attacker to read and write files on the underlying Linux system via crafted CLI commands.