Fortinet fixed two critical authentication-bypass vulnerabilities

Fortinet fixed two critical authentication-bypass vulnerabilities

Pierluigi Paganini
December 10, 2025

Fortinet patched 18 flaws, including two authentication-bypass bugs affecting FortiOS, FortiWeb, FortiProxy, and FortiSwitchManager with FortiCloud SSO enabled.

Fortinet addressed 18 vulnerabilities, including two authentication-bypass flaws, tracked as CVE-2025-59718 and CVE-2025-59719 (CVSS score of 9.1), affecting FortiOS, FortiWeb, FortiProxy, and FortiSwitchManager when FortiCloud SSO is enabled.

Both vulnerabilities are improper verification of cryptographic signature issues.

An improper signature-verification flaw in FortiOS, FortiWeb, FortiProxy, and FortiSwitchManager lets an unauthenticated attacker bypass FortiCloud SSO login using a crafted SAML message, if the feature is enabled. FortiCloud SSO is disabled by default, but it activates automatically during FortiCare registration unless the admin disables the “Allow administrative login using FortiCloud SSO” toggle.

“Please note that the FortiCloud SSO login feature is not enabled in default factory settings. However, when an administrator registers the device to FortiCare from the device’s GUI, unless the administrator disables the toggle switch “Allow administrative login using FortiCloud SSO” in the registration page, FortiCloud SSO login is enabled upon registration.” reads the advisory.

The vendor recommends disabling the FortiCloud login feature (if enabled) until upgrading to a non-affected version, as a temporary mitigation.

Below are the impacted versions:

The vulnerabilities were internally discovered and reported by Yonghui Han and Theo Leleu of Fortinet Product Security team.

At this time, it is unclear if any of these vulnerabilities has been exploited in attacks in the wild.

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