Fortinet FortiOS: information disclosure 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 an exposure of sensitive information to an unauthorized actor vulnerability. This may allow a remote unauthenticated attacker to bypass the patch developed for the symbolic link persistency mechanism observed in some post-exploit cases, via crafted HTTP requests. An attacker would need first to have compromised the product via another vulnerability, at filesystem level.

What an attacker can do

This is a information disclosure flaw. It lets an attacker read data they are not supposed to see, such as memory contents, credentials or internal files. It is often the first step of a larger attack.

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 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 mitigations in accordance with vendor instructions, ensuring compliance with CISA’s BOD 26-04 Prioritizing Security Updates Based on Risk (see URL in Notes) guidance and CISA’s “Forensics Triage Requirements” (see URL in Notes). Follow applicable BOD 26-04 guidance for cloud services or discontinue use of the product if mitigations are unavailable. Stakeholders are responsible for evaluating each asset's internet exposure and ensuring adherence to BOD 26-04 patching guidelines.

Vendor advisories and fixes

• fortiguard.fortinet.comfortiguard.fortinet.com/psirt/FG-IR-25-934

How urgent is it

CISA added this vulnerability to its Known Exploited Vulnerabilities catalogue on July 27, 2026, which means there is reliable evidence of attacks in the wild. US federal agencies must fix it by August 10, 2026, 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 29% 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 5.9 out of 10 (medium), as recorded in the US National Vulnerability Database.

Technical description

An Exposure of Sensitive Information to an Unauthorized Actor vulnerability [CWE-200] vulnerability in Fortinet FortiOS 7.6.0 through 7.6.1, FortiOS 7.4.0 through 7.4.6, FortiOS 7.2 all versions, FortiOS 7.0 all versions, FortiOS 6.4 all versions may allow a remote unauthenticated attacker to bypass the patch developed for the symbolic link persistency mechanism observed in some post-exploit cases, via crafted HTTP requests. An attacker would need first to have compromised the product via another vulnerability, at filesystem level.