CVE-2002-2245 in NetBSD
Summary
by MITRE
ftpd in NetBSD 1.5 through 1.5.3 and 1.6 does not properly quote a digit in response to a STAT command for a filename that contains a carriage return followed by a digit, which can cause firewalls and other intermediary devices to lose proper track of the FTP session.
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Analysis
by VulDB Data Team • 06/12/2018
The vulnerability identified as CVE-2002-2245 affects the ftpd implementation in NetBSD operating systems versions 1.5 through 1.5.3 and 1.6. This issue stems from improper handling of special characters in FTP responses, specifically when processing STAT commands for filenames containing carriage return followed by a digit sequences. The flaw represents a classic case of inadequate input sanitization and output formatting that can lead to significant operational disruptions in networked environments.
The technical root cause lies in how the ftpd daemon processes and formats responses to STAT commands when filenames contain specific character sequences. When a filename includes a carriage return character followed immediately by a digit, the response generation process fails to properly quote or escape these special characters. This improper quoting creates ambiguous response sequences that can confuse intermediary network devices, particularly firewalls and NAT appliances, which rely on parsing FTP control channel responses to maintain session state and connection tracking. The vulnerability maps to CWE-174, which deals with inadequate input sanitization leading to improper output formatting, and specifically relates to the broader category of improper handling of special characters in protocol implementations.
The operational impact of this vulnerability extends beyond simple session disruption to potentially compromise network security and reliability. Firewalls and other intermediary devices that perform stateful packet inspection rely on consistent and predictable FTP response formats to maintain accurate session tracking. When the ftpd daemon generates malformed responses due to improper quoting, these devices may misinterpret the session state, leading to connection drops, failed transfers, or even potential security bypasses where malicious actors could exploit the confusion to manipulate network traffic. The issue affects the fundamental reliability of FTP services in environments where network intermediaries are present, making it particularly concerning for enterprise deployments and internet-facing services.
Mitigation strategies for this vulnerability should focus on both immediate patching and operational hardening measures. The most effective solution involves upgrading to NetBSD versions that contain the fix for this specific quoting issue, as the vulnerability was addressed in subsequent releases. Organizations should also implement network monitoring to detect anomalous FTP behavior that might indicate exploitation attempts. Additionally, network administrators should consider implementing FTP protocol filtering rules that can detect and block malformed responses, though such measures must be carefully balanced against legitimate network operations. The vulnerability demonstrates the importance of proper input validation and output formatting in network protocol implementations, aligning with ATT&CK technique T1071.004 for application layer protocol manipulation and emphasizing the need for robust security practices in network service implementations. Organizations should also conduct regular security assessments of their network infrastructure to identify similar issues in other protocol implementations that might create comparable session tracking problems.