CVE-2002-1979 in SOHO
Summary
by MITRE
WatchGuard SOHO products running firmware 5.1.6 and earlier, and Vclass/RSSA using 3.2 SP1 and earlier, allows remote attackers to bypass firewall rules by sending a PASV command string as the argument of another command to an FTP server, which generates a response that contains the string, causing IPFilter to treat the response as if it were a legitimate PASV command from the server.
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Analysis
by VulDB Data Team • 07/07/2024
This vulnerability exists in WatchGuard SOHO firewall products and Vclass/RSSA systems running specific firmware versions where the IPFilter component fails to properly validate FTP responses. The flaw stems from inadequate input sanitization and command parsing within the firewall's FTP inspection mechanism. When an attacker sends a maliciously crafted command containing a PASV command string as an argument, the system processes this input without proper validation, leading to a situation where the response contains the PASV string. This malformed response triggers the IPFilter to incorrectly interpret the response as a legitimate PASV command from the FTP server, thereby bypassing the firewall's rule enforcement mechanisms.
The technical implementation of this vulnerability exploits a fundamental weakness in the firewall's stateful inspection capabilities and demonstrates a classic case of command injection within protocol parsing. The vulnerability allows remote attackers to manipulate the firewall's internal state machine by crafting specific command sequences that cause the system to misinterpret network traffic. This represents a failure in proper input validation and command argument handling, which aligns with CWE-20 - Improper Input Validation and CWE-77 - Command Injection. The flaw specifically affects the FTP protocol inspection module where the firewall attempts to parse and validate FTP responses while maintaining connection state information.
The operational impact of this vulnerability is significant as it allows attackers to completely bypass firewall rules that would normally protect internal network resources from unauthorized FTP access. An attacker can leverage this weakness to establish unauthorized connections, potentially gaining access to internal systems that should be protected by the firewall's rule set. The bypass occurs at the network level where the firewall's filtering rules are effectively neutralized, creating a persistent backdoor for malicious activities. This vulnerability could enable attackers to perform reconnaissance, data exfiltration, or establish further footholds within the network infrastructure, making it particularly dangerous in enterprise environments where firewall protection is critical.
Mitigation strategies should focus on immediate firmware updates to versions that address the input validation issues in the FTP inspection module. Network administrators should also implement additional monitoring of FTP traffic patterns to detect anomalous command sequences that might indicate exploitation attempts. The firewall configuration should include stricter inspection rules for FTP protocol handling and enhanced logging of suspicious command arguments. Organizations should consider implementing network segmentation and access control lists as additional defensive measures to limit the potential impact of such bypasses. This vulnerability highlights the importance of proper input validation in network security appliances and underscores the need for comprehensive testing of protocol handling mechanisms against injection attacks. The remediation process should also include reviewing and updating security policies to address similar weaknesses in other protocol inspection modules that may be vulnerable to similar command injection attacks.