Fortinet’s FortiCloud SSO Bypass: A Critical Security Alert for FortiOS, FortiWeb, and FortiProxy Users

In the complex landscape of enterprise cybersecurity, Single Sign-On (SSO) solutions are paramount, offering streamlined access and enhanced security. However, recent findings have unveiled a critical vulnerability within Fortinet’s FortiCloud SSO authentication, directly impacting a range of their widely deployed products. This flaw could allow unauthorized access, posing a significant risk to organizations relying on these systems. Understanding the nature of this vulnerability and implementing timely remediation is not just recommended, it’s essential.

The Critical Vulnerability: Improper Verification of Cryptographic Signature

Fortinet has issued an urgent security advisory concerning a severe vulnerability, CVE-2023-45582 (https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2023-45582), specifically categorized as an Improper Verification of Cryptographic Signature (CWE-347). This weakness is present across multiple Fortinet product lines, including FortiOS, FortiWeb, and FortiProxy. The core issue lies in the device’s failure to adequately verify cryptographic signatures during the FortiCloud SSO authentication process.

An unauthenticated attacker could exploit this defect to bypass the FortiCloud SSO login authentication. This means a malicious actor, without needing any prior credentials, could potentially gain unauthorized access to an organization’s network or critical applications secured by these Fortinet products. The implications of such a bypass are far-reaching, from data exfiltration to complete system compromise, depending on the role and privileges associated with the bypassed authentication.

Affected Fortinet Products

The vulnerability pertains to the following Fortinet products when configured to use FortiCloud SSO:

• FortiOS: Versions 7.0.0 through 7.0.12, 7.2.0 through 7.2.5, and 7.4.0 through 7.4.1.
• FortiWeb: Versions 7.0.0 through 7.0.8, and 7.2.0 through 7.2.2.
• FortiProxy: Versions 7.0.0 through 7.0.10, and 7.2.0 through 7.2.4.
• FortiSwitchManager: While the primary advisory text linked may not explicitly mention FortiSwitchManager for this specific CVE, similar SSO vulnerabilities often affect a broader range of Fortinet products leveraging shared authentication mechanisms. Always refer to official Fortinet advisories for the most accurate and up-to-date list.

Organizations utilizing any of these product versions with FortiCloud SSO enabled are at risk and should prioritize immediate action.

Understanding CWE-347: Improper Verification of Cryptographic Signature

CWE-347 describes a situation where an application fails to properly verify that a cryptographic signature is valid. In the context of SSO, this typically means that the system is presented with an authentication token or assertion that claims to be from a trusted source (like FortiCloud), but the system either doesn’t check the signature at all, or performs an insufficient check. An attacker can then forge a signature or reuse an old one, tricking the system into believing the assertion is legitimate. This flaw fundamentally undermines the trust mechanism that security protocols rely on for authentication.

Remediation Actions: Immediate Steps to Secure Your Fortinet Deployments

Given the critical nature of this vulnerability, immediate remediation is imperative. Fortinet has released patches to address CVE-2023-45582. Organizations should:

• Upgrade Immediately: Apply the latest available patches for all affected Fortinet products. Refer to Fortinet’s official security advisory for precise version numbers and upgrade paths. This is the most effective and recommended solution.
• Review SSO Configurations: Even after patching, conduct a thorough review of your FortiCloud SSO configurations to ensure best practices are followed and no other misconfigurations exist that could expose your systems.
• Monitor Logs: Increase vigilance in monitoring authentication logs for unusual login attempts or unexpected access, especially those originating from outside your typical network boundaries.
• Implement Multi-Factor Authentication (MFA): While not a direct fix for this specific bypass, ensuring robust MFA is enforced across all administrative and critical user accounts adds an additional layer of security that can mitigate the impact of certain authentication bypasses.
• Network Segmentation: Ensure critical systems are isolated through network segmentation, limiting an attacker’s lateral movement even if initial access is gained.

Relevant Security Tools for Detection and Mitigation

Here’s a table of useful tools that can aid in identifying vulnerabilities and strengthening your security posture:

Tool Name	Purpose	Link
Nessus	Vulnerability Scanning and Management	https://www.tenable.com/products/nessus
OpenVAS	Open-source Vulnerability Scanner	http://www.openvas.org/
FortiAnalyzer	Centralized Logging, Analytics, and Reporting for Fortinet Devices	https://www.fortinet.com/products/security-fabric/fortianalyzer
Security Information and Event Management (SIEM) solutions (e.g., Splunk, QRadar)	Centralized log collection, analysis, and alerting for detecting suspicious activity	https://www.splunk.com/

Protecting Your Perimeter: A Continuous Effort

This Fortinet vulnerability underscores the continuous threat landscape faced by organizations globally. The ability for an unauthenticated attacker to bypass FortiCloud SSO authentication across critical Fortinet products like FortiOS, FortiWeb, and FortiProxy presents a significant attack vector. Prompt patching, diligent security monitoring, and adherence to best practices for identity and access management are non-negotiable in maintaining a robust security posture against such sophisticated threats. Staying informed through official vendor advisories and proactively implementing security updates are crucial defenses in safeguarding your digital assets.