CVE-2006-3222 in FortiOS
Summary
by MITRE
The FTP proxy module in Fortinet FortiOS (FortiGate) before 2.80 MR12 and 3.0 MR2 allows remote attackers to bypass anti-virus scanning via the Enhanced Passive (EPSV) FTP mode.
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Analysis
by VulDB Data Team • 07/29/2018
The vulnerability described in CVE-2006-3222 represents a critical security flaw within the Fortinet FortiOS FTP proxy module that affects versions prior to 2.80 MR12 and 3.0 MR2. This weakness specifically targets the handling of Enhanced Passive (EPSV) FTP mode connections, which is a standard extension to the traditional FTP protocol designed to improve connectivity through firewalls and NAT environments. The vulnerability allows remote attackers to circumvent the built-in anti-virus scanning capabilities that are typically enforced by the FortiGate firewall's FTP proxy functionality, potentially enabling malicious content to bypass security controls.
The technical implementation of this vulnerability stems from the improper handling of EPSV commands within the FTP proxy module's connection processing logic. When an FTP client establishes a connection using EPSV mode, the proxy module should maintain consistent inspection and scanning of data transfers. However, the flaw in affected FortiOS versions causes the system to skip anti-virus scanning for certain EPSV-based data connections, creating a bypass mechanism that attackers can exploit. This occurs because the proxy module fails to properly correlate the control connection with the data connection in EPSV mode, allowing malicious payloads to flow through the firewall without the expected security checks.
The operational impact of this vulnerability extends beyond simple bypass of anti-virus protection, as it represents a significant weakness in the network security posture of organizations relying on FortiGate firewalls for content filtering. Attackers can leverage this vulnerability to deliver malware, exploit payloads, or other malicious content that would normally be detected and blocked by the firewall's anti-virus scanning capabilities. This creates a persistent threat vector that could allow attackers to establish command and control channels, exfiltrate sensitive data, or deploy additional malware within the network environment without detection. The vulnerability particularly affects organizations that depend on FTP proxy scanning as part of their security architecture for protecting against file-based threats.
Organizations should implement immediate mitigations including upgrading to FortiOS versions 2.80 MR12 or 3.0 MR2, which contain the necessary patches to address this vulnerability. Network administrators should also consider implementing additional monitoring and logging mechanisms to detect anomalous FTP traffic patterns that might indicate exploitation attempts. The vulnerability aligns with CWE-284 Access Control Issues, specifically relating to improper access control in network protocol handling, and can be categorized under ATT&CK technique T1071.004 Application Layer Protocol: FTP. Security teams should also review their firewall configurations to ensure that alternative security controls are in place to compensate for the bypass capability, including implementing network segmentation, additional content inspection mechanisms, and enhanced network monitoring to detect potential exploitation attempts.