CVE-2026-104286: Fortinet FortiMail Path Traversal Vulnerability
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
Treat this as urgent. Identify every affected system, starting with anything internet-facing, and apply the vendor fix or mitigation within days. If you cannot patch quickly, isolate or disable the affected service and watch for signs of compromise.
- Priority
- Act now: Patch or mitigate internet-facing systems within days.
- Severity (CVSS)
- 9.8 critical
- CISA assessment (SSVC)
- actively exploited; attackers can automate it at scale; total control of the affected system
- Exploit probability (EPSS, 30 days)
- 2.2%, higher than 82% of all CVEs
- Added to CISA KEV
- 1 October 2026
- CISA fix-by date
- 4 October 2026 (US federal agencies; a sensible deadline for everyone)
- Ransomware use
- Not known
- Weakness
- CWE-22
References
- NIST NVD entry
- CISA KEV entry
- fortiguard.fortinet.com/psirt/FG-IR-26-175
- www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-104286
Sources: CISA Known Exploited Vulnerabilities · FIRST Exploit Prediction Scoring System (EPSS) · NIST National Vulnerability Database · CISA Vulnrichment (SSVC), via the CVE Program. This product uses data from the NVD API but is not endorsed or certified by the NVD. Summaries are machine-written from CISA’s description; treat the vendor’s advisory as the authority for fixes.