CVE-2002-1978 in IPFilter
Summary
by MITRE
IPFilter 3.1.1 through 3.4.28 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
The vulnerability described in CVE-2002-1978 represents a significant security flaw in IPFilter firewall software versions 3.1.1 through 3.4.28 that enables remote attackers to circumvent network security controls through a sophisticated command injection technique. This issue arises from the improper handling of FTP protocol responses within the firewall's parsing logic, creating a pathway for malicious actors to manipulate firewall behavior through carefully crafted network traffic. The vulnerability specifically targets the Passive FTP mode handling mechanism, which is a standard feature of the File Transfer Protocol designed to facilitate data connections between FTP clients and servers.
The technical root cause of this vulnerability stems from IPFilter's failure to properly sanitize and validate response strings received from FTP servers during the command processing phase. When an attacker sends a malicious PASV command string as an argument to another FTP command, the system processes this input without adequate filtering mechanisms. The firewall software then treats the response containing this injected string as if it were an authentic PASV command from the legitimate FTP server, thereby allowing unauthorized network access. This represents a classic case of command injection where attacker-controlled data is interpreted as executable instructions within the firewall's processing pipeline, violating fundamental security principles of input validation and sanitization.
The operational impact of this vulnerability extends beyond simple firewall bypass, creating potential for extensive network compromise and data exfiltration. An attacker exploiting this flaw can effectively circumvent network security controls that rely on IPFilter to enforce access policies, potentially gaining unauthorized access to protected network segments. The vulnerability affects the integrity of the firewall's rule enforcement mechanism, as the malicious response string can be interpreted by IPFilter's stateful inspection engine as legitimate server communication. This creates a persistent security weakness that can be exploited repeatedly, as the attacker only needs to craft the appropriate malicious command sequence once to establish the bypass condition. The vulnerability also demonstrates the importance of proper protocol state management and response parsing in network security appliances.
Mitigation strategies for this vulnerability should focus on immediate software updates to the latest IPFilter versions that address the command injection flaw, as well as implementing additional network monitoring and anomaly detection measures. Organizations should consider deploying network segmentation strategies to limit the potential impact of such bypasses, while also implementing comprehensive logging and audit mechanisms to detect unauthorized access attempts. The vulnerability aligns with CWE-74 standards for injection flaws and relates to ATT&CK technique T1071.004 for application layer protocol tunneling, highlighting the need for robust input validation and protocol compliance checking in security appliances. Network administrators should also consider implementing intrusion detection systems that can identify suspicious FTP command sequences and response patterns that may indicate exploitation attempts.