FortiMail Zero-Day Vulnerability Actively Exploited, CISA Mandates Remediation

A critical zero-day vulnerability (CVE-2026-104286) in Fortinet's FortiMail email security gateway is under active exploitation. CISA added this flaw to its Known Exploited Vulnerabilities catalog, requiring federal agencies to apply workarounds or patches by October 4, 2026. This vulnerability allows unauthenticated attackers to write arbitrary files, posing a significant security risk without an official patch yet available.