CVE-2026-104286

Vulnerability details

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.

Added to CISA KEV: 2026-10-01

Ransomware campaign use: Unknown

CISA due date: 2026-10-04

Defensive guidance from CISA

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.

This is the source's required-action field, not an independently validated patch procedure. Refer to the vendor for exact affected versions and fixes.