CVE-2023-47539 in FortiMail
Summary
by MITRE • 03/18/2025
An improper access control vulnerability in FortiMail version 7.4.0 configured with RADIUS authentication and remote_wildcard enabled may allow a remote unauthenticated attacker to bypass admin login via a crafted HTTP request.
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Analysis
by VulDB Data Team • 07/25/2025
This vulnerability represents a critical improper access control flaw in FortiMail version 7.4.0 that specifically impacts systems utilizing RADIUS authentication with the remote_wildcard configuration enabled. The issue stems from inadequate validation of authentication requests, allowing unauthorized actors to exploit a path traversal mechanism within the web interface. The vulnerability is classified under CWE-285, which specifically addresses improper access control, and aligns with ATT&CK technique T1078.101 for Valid Accounts and T1190 for Exploit Public-Facing Application. When RADIUS authentication is configured alongside remote_wildcard functionality, the system fails to properly validate the authenticity of incoming requests, creating a potential backdoor for malicious actors.
The technical implementation of this flaw occurs through a crafted HTTP request that manipulates the authentication flow by exploiting how the system processes wildcard patterns in remote access configurations. Attackers can construct specific requests that bypass the normal administrative login process, effectively gaining unauthorized access to administrative functions without requiring valid credentials. This occurs because the remote_wildcard feature, when enabled, creates a relaxed validation mechanism that does not adequately verify the legitimacy of authentication attempts. The vulnerability is particularly concerning as it requires no prior authentication credentials and can be exploited remotely, making it accessible to any attacker with network access to the affected system.
The operational impact of this vulnerability extends beyond simple unauthorized access, as it could enable attackers to execute arbitrary commands, modify system configurations, access sensitive email data, and potentially establish persistent access to the mail server. Administrative privileges gained through this vulnerability could allow attackers to read, modify, or delete email messages, alter user accounts, configure system settings, and potentially use the compromised FortiMail server as a staging point for further attacks within the network. The risk is amplified by the fact that this vulnerability affects the core authentication mechanism, potentially compromising the entire email infrastructure and exposing organizations to data breaches, email spoofing, and other malicious activities.
Organizations should immediately implement mitigations including disabling the remote_wildcard feature when RADIUS authentication is in use, applying the latest FortiMail patches provided by Fortinet, and implementing network segmentation to limit access to the FortiMail server. Additional protective measures should include monitoring for unusual authentication patterns, implementing strict access controls for administrative interfaces, and conducting regular security assessments of authentication mechanisms. The vulnerability demonstrates the importance of proper input validation and access control implementation, particularly in systems handling sensitive communications. Organizations should also consider implementing multi-factor authentication for administrative access and regularly reviewing authentication configurations to ensure that features like remote_wildcard are only enabled when absolutely necessary for legitimate business operations.