FortiMail

Fortinet Releases FortiMail Updates to Patch Zero-Day CVE-2026-104286

Fortinet has begun distributing updates for its FortiMail email security product to address the zero-day vulnerability CVE-2026-104286. The flaw allows unauthenticated attackers to write arbitrary files to the system by sending specially crafted HTTP requests. The company first published a security advisory on October 1, 2026, confirming active exploitation and providing Indicators of Compromise while preparing fixes. On October 5, 2026, Fortinet updated the advisory and released patched versions including FortiMail 8.0.2, 7.6.7, and 7.4.9. Organizations still running the 7.2 branch are advised to migrate to the 7.4 branch or later to obtain protection. The advisory reference is FG-IR-26-175.

Critical Zero-Day Vulnerability in FortiMail Allows Unauthenticated File Writes

Fortinet disclosed a critical zero-day vulnerability in its FortiMail email security product that is already being exploited in attacks. The flaw, tracked as CVE-2026-104286, affects the graphical user interface component and stems from improper sanitization of path traversal and NULL byte sequences. Attackers can craft malicious HTTP requests to write arbitrary files to the system without authentication. The vulnerability received a CVSS v3.1 base score of 9.8, classifying it as Critical. Fortinet discovered the issue internally but has also received reports of active exploitation. Planned patches include FortiMail 8.0.2, 7.6.7, and 7.4.9, while users on the 7.2 branch are advised to migrate to 7.4 or later.