CVE-2005-3057 in FortiOS
Summary
by MITRE
The FTP component in FortiGate 2.8 running FortiOS 2.8MR10 and v3beta, and other versions before 3.0 MR1, allows remote attackers to bypass the Fortinet FTP anti-virus engine by sending a STOR command and uploading a file before the FTP server response has been sent, as demonstrated using LFTP.
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Analysis
by VulDB Data Team • 07/16/2018
The vulnerability described in CVE-2005-3057 represents a critical flaw in the FortiGate firewall's FTP handling mechanism that fundamentally undermines the security posture of the device. This issue affects FortiGate appliances running FortiOS versions 2.8MR10 and v3beta, as well as other pre-3.0 MR1 releases, creating a window of opportunity for attackers to circumvent essential security controls. The vulnerability specifically targets the anti-virus engine functionality within the FTP component, which is designed to scan and block malicious files transferred through the firewall. The flaw exploits a timing discrepancy in the FTP protocol implementation where the system fails to properly validate file uploads before completing the server response process. This timing gap creates an exploitable condition that allows malicious actors to inject files directly into the system without undergoing the standard antivirus scanning procedures that would normally occur during the upload process.
The technical exploitation of this vulnerability involves leveraging the STOR command within the File Transfer Protocol to upload files to the FTP server while the server is still processing the previous command response. This specific timing attack demonstrates how attackers can manipulate the FTP state machine to bypass security controls before the system has completed its normal processing sequence. The LFTP demonstration shows that this vulnerability can be reliably exploited using standard FTP client tools, making it particularly dangerous as it requires no specialized attack tools beyond what is already available in standard security testing suites. The flaw essentially allows for a race condition scenario where the file upload occurs before the antivirus engine has had sufficient time to process the file, resulting in the execution of potentially malicious content that would otherwise be blocked by security policies.
The operational impact of this vulnerability extends beyond simple bypass of antivirus protection, as it represents a fundamental failure in the security architecture of the FortiGate appliance. Organizations relying on these devices for network protection face significant risks including potential malware infections, unauthorized data access, and complete compromise of the firewall's security functions. The vulnerability affects the core security controls that administrators expect to be in place, creating a false sense of security where network traffic appears to be properly scanned and filtered while actually allowing malicious content to pass through undetected. This flaw undermines the trust model of the firewall as a security gateway and could enable attackers to establish persistent access points within the network infrastructure. The vulnerability also demonstrates poor implementation of security controls that should be enforced at the protocol level rather than relying on timing-based defenses that can be easily circumvented.
Mitigation strategies for this vulnerability require immediate patching of affected FortiGate appliances to versions 3.0 MR1 or later where the security flaw has been addressed through proper implementation of the FTP protocol handling. Organizations should implement network segmentation and additional monitoring controls to detect anomalous FTP traffic patterns that might indicate exploitation attempts. The vulnerability highlights the importance of proper protocol implementation and the need for thorough testing of security controls under various timing conditions. Security teams should also consider implementing additional layers of protection such as deep packet inspection and behavioral analysis to detect and prevent exploitation attempts. This vulnerability serves as a reminder of the critical importance of maintaining up-to-date security firmware and the necessity of comprehensive security testing that includes timing-based attack scenarios. From an industry standards perspective, this vulnerability aligns with CWE-362, which addresses race conditions, and relates to ATT&CK techniques involving privilege escalation and persistence through file manipulation. The flaw demonstrates how inadequate input validation and improper state management can create security vulnerabilities that bypass fundamental protection mechanisms.