Fortinet FortiCloud SSO Login Authentication Bypass: What You Need to Know
Fortinet has issued a critical advisory on December 9, 2025 concerning two severe authentication‑bypass vulnerabilities that affect a broad spectrum of Fortinet devices, from FortiOS and FortiProxy to FortiWeb and FortiSwitchManager. The flaws-CVE‑2025‑59718 and CVE‑2025‑59719-enable attackers to sidestep FortiCloud Single‑Sign‑On (SSO) authentication by submitting a malicious SAML message that exploits a weakness in cryptographic signature verification. Below is a concise breakdown of the threat, its impact, and the steps you can take to protect your environment. 1. What the Vulnerabilities Are Fortinet's FortiCloud SSO feature, when enabled, relies on SAML tokens to authenticate administrators. The vulnerabilities arise because the devices improperly verify the signature of those tokens. If an attacker can craft a forged SAML assertion that the device accepts as valid, they can gain administrative access without knowing any legitimate credentials. CVE‑2025‑59718 affects FortiOS, FortiProxy, and FortiSwitchManager. CVE‑2025‑59719 targets FortiWeb's SSO implementation. Both issues can be exploited only when the FortiCloud…
