Fortinet FortiOS authentication bypass impacts FortiCloud SSO
Fortinet disclosed critical authentication bypass vulnerabilities (CVE-2025-59718, CVE-2025-59719) in FortiOS, FortiWeb, FortiProxy, and FortiSwitchManager affecting FortiCloud SSO login.
Sourceipa.go.jp — open the original
What to check
- Applies to
- The 2 CVEs named below. Whether you run an affected version is not assessed: check the versions the source lists.
- Exploitation
- CISA lists CVE-2025-59718 as exploited in the wild.
Japan's IPA (Information-technology Promotion Agency) published an alert regarding multiple Fortinet products affected by improper digital signature verification vulnerabilities. CVE-2025-59718 and CVE-2025-59719 impact FortiOS, FortiWeb, FortiProxy, and FortiSwitchManager. Unauthenticated remote attackers can exploit these flaws to bypass authentication when FortiCloud SSO login functionality is enabled.
Fortinet's CVSS assessment indicates that exploit code already exists for these vulnerabilities, heightening the urgency. The FortiCloud SSO login feature is enabled by default when devices are registered via the GUI in FortiCare unless administrators explicitly disable the "Allow administrative login using FortiCloud SSO" option during registration.
Fortinet has released patched versions addressing both vulnerabilities. IPA recommends immediate upgrading to the latest versions following Fortinet's published procedures. As an interim measure, administrators can mitigate risk by disabling the FortiCloud SSO login feature if not required for operations.
Mentioned in this report
Source reporting: https://www.ipa.go.jp/security/security-alert/2025/alert20251217.html
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