CVE-2002-0104 in AFTPD
Summary
by MITRE
AFTPD 5.4.4 allows remote attackers to gain sensitive information via a CD (CWD) ~ (tilde) command, which causes a core dump.
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Analysis
by VulDB Data Team • 05/13/2019
The vulnerability identified as CVE-2002-0104 affects AFTPD version 5.4.4, a file transfer protocol daemon that provides ftp services for unix systems. This issue represents a significant security flaw that allows remote attackers to exploit a specific command sequence within the ftp protocol implementation. The vulnerability specifically manifests when a malicious user sends a CD command followed by a tilde character, which triggers an unexpected behavior in the daemon's processing logic.
The technical root cause of this vulnerability lies in the improper handling of user input within the AFTPD daemon's command processing subsystem. When the daemon receives the CD command combined with a tilde character, it fails to properly validate or sanitize the input before processing it. This lack of input validation creates a condition where the daemon attempts to interpret the malformed command sequence in a way that leads to an abnormal termination state. The resulting core dump contains sensitive information from the daemon's memory space, including potentially confidential data that should not be exposed to unauthorized users.
The operational impact of this vulnerability extends beyond simple information disclosure, as it provides attackers with a means to gather potentially sensitive system information that could aid in further exploitation attempts. The core dump file generated by this vulnerability may contain memory contents including user credentials, system configuration details, or other confidential information that could be valuable to an attacker. This information disclosure vulnerability falls under the category of CWE-20 Improper Input Validation, which is a fundamental weakness that allows attackers to manipulate input to cause unintended behavior in applications.
From an attack perspective, this vulnerability demonstrates a classic example of how improper error handling and input validation can lead to information exposure. The attack requires minimal privileges as it only requires access to the ftp service, making it particularly dangerous for systems that expose ftp services to untrusted networks. The vulnerability aligns with ATT&CK technique T1083 (File and Directory Discovery) and T1005 (Data from Local System) as attackers can leverage this flaw to extract system information without requiring elevated privileges.
The mitigation strategy for this vulnerability involves immediate patching of the AFTPD daemon to version 5.4.5 or later, which contains the necessary fixes for input validation and command processing. System administrators should also implement network segmentation to limit access to ftp services, particularly when they are exposed to untrusted networks. Additionally, monitoring for unusual ftp command sequences and core dump generation should be implemented to detect potential exploitation attempts. The fix typically involves implementing proper input validation routines that reject malformed command sequences before they can be processed by the daemon, thereby preventing the core dump generation and subsequent information disclosure. Organizations should also consider implementing additional security controls such as ftp service restrictions, access control lists, and regular security auditing of ftp services to prevent similar vulnerabilities from being exploited in other components of their infrastructure.