Known exploited vulnerability · CISA KEV

CVE-2026-104286: Fortinet FortiMail Path Traversal Vulnerability

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.

CVE-2026-104286

Exploited in the wild. Fix this first.

CISA added it to the Known Exploited Vulnerabilities catalog on 2026-10-01: attackers are using it right now.

CISA KEV: Listed; Added 2026-10-01 · federal fix-by 2026-10-04
EPSS (30 days): 4.6%; Higher than 92% of CVEs · 2026-11-01
CVSS v3.1: 9.8 Critical; CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

What CISA says

Fortinet FortiMail Path Traversal Vulnerability

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.

NVD description · published 2026-10-01

An improper limitation of a pathname to a restricted directory ('path traversal') vulnerability in Fortinet FortiMail 8.0.0 through 8.0.1, FortiMail 7.6.0 through 7.6.6, FortiMail 7.4.0 through 7.4.8, FortiMail 7.2.0 through 7.2.9, FortiMail 7.0 all versions may allow an unauthenticated attacker to write arbitrary files on the underlying system via crafted HTTP or HTTPS requests.

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How to check if you are exposed to CVE-2026-104286

Find every Fortinet FortiMail system you or your clients run, including ones exposed to the internet. Those come first: CISA only lists flaws attackers are already using.
Compare each version with the fixed versions in the vendor advisory below. Where no fix exists yet, apply the vendor’s mitigation or take the system off the internet.
Run a credentialed vulnerability scan to catch the systems you missed, then check that the next scan no longer reports CVE-2026-104286.

US federal agencies had to fix this by 2026-10-04. Everyone else should treat that deadline as a guide: if it has passed, this is overdue.

Affected versions

Versions the National Vulnerability Database lists as vulnerable to CVE-2026-104286. Check the vendor advisory for the exact fixed builds before you sign anything off.

Product	Vulnerable versions
Fortinet Fortimail	from 7.0.0 up to and including 7.0.9; from 7.2.0 up to and including 7.2.9; from 7.4.0 before 7.4.9; from 7.6.0 before 7.6.7; from 8.0.0 before 8.0.2

Timeline

2026-10-01 · Published in the National Vulnerability Database
2026-10-01 · Added to CISA's Known Exploited Vulnerabilities catalog, the same day it was published
2026-10-04 · Fix-by date for US federal agencies, passed 28 days ago

Vendor advisories and fixes

https://fortiguard.fortinet.com/psirt/FG-IR-26-175

Weakness type

More exploited Fortinet vulnerabilities

CISA lists 32 exploited Fortinet vulnerabilities. The closest matches:

Keep going

Sources: CISA Known Exploited Vulnerabilities catalog (version 2026.10.30); EPSS data from FIRST.org; CVSS and descriptions from the NIST National Vulnerability Database. Checked 2026-11-01. This product uses the NVD API but is not endorsed or certified by the NVD.