Exploited vulnerability · CISA KEV

Is CVE-2026-104286 exploited? Yes: in CISA KEV since 1 Oct 2026

Gociux · Fortinet FortiMail · data: CISA KEV, CVE record, FIRST EPSS

Yes. CVE-2026-104286, Fortinet FortiMail Path Traversal Vulnerability, is being exploited in the wild. CISA added it to its Known Exploited Vulnerabilities catalog on 1 Oct 2026, the day it was published. It affects Fortinet FortiMail, an internet-facing product of the kind attackers use for initial access. If you run it, CISA's required action is: 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.

What it is

Fortinet FortiMail contains a path traversal and an improper neutralization of NULL byte or NULL character vulnerability that may allow an unauthenticated attacker to write arbitrary files on the underlying system via crafted HTTP or HTTPS requests.

What to do

1. Check whether you run it. Look for FortiMail in your asset inventory, including appliances and cloud images. Stack check lists every exploited Fortinet CVE at once.
2. Apply the fix. 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.
3. If you can't patch today, take the affected service off the internet or restrict who can reach it, and check its logs for signs of compromise since 1 Oct 2026.
4. Get told next time. Email alerts when CISA adds a CVE for Fortinet.

References

• fortiguard.fortinet.com/psirt/FG-IR-26-175
• nvd.nist.gov/vuln/detail/CVE-2026-104286

Sources: CISA KEV (exploitation, ransomware use, required action, due date), the CVE record (publication date, CVSS, CNA), NVD and FIRST EPSS (live score). More: all KEV additions in October 2026 · Fortinet scorecard · act-now radar.