How to fix CVE-2026-104286: Fortinet FortiMail (exploited in the wild)

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 may allow an unauthenticated attacker to write arbitrary files on the underlying system via crafted HTTP or HTTPS requests.

• Severity: CRITICAL (CVSS 3.1 9.8, vector CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H).
• Weakness: CWE-22, CWE-158.
• NVD published 2026-10-01, status Analyzed.

Anyone running Fortinet FortiMail in the version ranges below. Internet-facing instances are the priority.

• fortinet fortimail: from 7.2.0 up to and including 7.4.8.
• fortinet fortimail: from 7.6.0 up to and including 7.6.6.
• fortinet fortimail: from 8.0.0 up to and including 8.0.1.

Version ranges come from the NVD CPE configuration. Confirm against the vendor advisory before you rely on them.

• Exploited in the wild: added to the CISA Known Exploited Vulnerabilities catalog on 2026-10-01; federal remediation due date 2026-10-04.
• Public proof-of-concept code: 4 GitHub repositories from 4 accounts, the first on 2026-10-01.

• EPSS (probability of exploitation activity in the next 30 days): 2.20%, higher than 82% of all scored CVEs (as of 2026-10-24).
• CVERadar threat level: 65/100 (see methodology).
• Likely ATT&CK techniques: T1190 Exploit Public-Facing Application (inferred); T1083 File and Directory Discovery (inferred).

1. Find every instance. List where Fortinet FortiMail runs, including test, DR and forgotten internet-facing systems, and record the installed version.

   get system status

2. Apply the latest vendor update. NVD does not list a fixed version, so follow the vendor advisory for the patched release.
3. If you can't patch today, follow CISA's required action: 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.
4. Verify the fix. Re-run the version check above on every instance and confirm it reports the fixed build. Re-scan from outside if the service is exposed.
5. Hunt for signs of earlier compromise. If the system was exposed before you patched, assume it may have been hit and check the items below.
6. Rotate credentials stored on or used by the affected system if you cannot rule out compromise, and keep the logs you reviewed.

Detection hints

• T1190 Exploit Public-Facing Application: Review WAF, reverse-proxy and application logs for unusual requests to FortiMail (odd paths, oversized or encoded payloads, bursts of errors), going back to at least 2026-10-01.

Detection commands are generic starting points, not CVE-specific signatures. Use the indicators from the vendor advisory when it publishes them.

• NVD: CVE-2026-104286 nvd.nist.gov/vuln/detail/CVE-2026-104286
• CVE.org record www.cve.org/CVERecord?id=CVE-2026-104286
• Vendor link from CISA KEV fortiguard.fortinet.com/psirt/FG-IR-26-175
• CISA KEV catalog www.cisa.gov/known-exploited-vulnerabilities-catalog
• FIRST EPSS (2026-10-24) api.first.org/data/v1/epss?cve=CVE-2026-104286