CVE-2000-0761 in OS2
Summary
by MITRE
OS2/Warp 4.5 FTP server allows remote attackers to cause a denial of service via a long username.
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Analysis
by VulDB Data Team • 05/27/2018
The vulnerability identified as CVE-2000-0761 affects the OS2/Warp 4.5 FTP server implementation, representing a classic buffer overflow condition that can be exploited to induce a denial of service scenario. This issue stems from inadequate input validation within the server's authentication handling mechanism, where the system fails to properly sanitize or limit the length of username parameters submitted during the login process. The flaw exists at the protocol level where the FTP server processes user credentials without implementing proper bounds checking on the username field, allowing malicious actors to craft specially crafted login requests containing excessively long username strings. When the server attempts to process these oversized inputs, the buffer overflow condition occurs, causing the FTP service to crash or become unresponsive, thereby preventing legitimate users from accessing the system resources.
This vulnerability directly maps to CWE-121, which describes the classic stack-based buffer overflow condition, and also relates to CWE-122, which addresses heap-based buffer overflows that can occur when insufficient bounds checking is performed on input data. The operational impact of this vulnerability extends beyond simple service disruption as it represents a fundamental security weakness in the server's input handling architecture. Attackers can leverage this flaw to perform persistent denial of service attacks against FTP services running on OS2/Warp 4.5 systems, potentially causing extended downtime for critical file transfer operations. The vulnerability is particularly concerning because it requires minimal technical expertise to exploit, making it attractive to threat actors seeking to disrupt service availability. The attack surface is limited to the FTP protocol interface, but the impact can be significant for organizations relying on this legacy system for file transfers and data exchange operations.
The technical exploitation of this vulnerability follows the ATT&CK framework's T1499.004 technique for network denial of service, where adversaries target network services to make them unavailable to legitimate users. The attack vector involves sending a malformed FTP login request containing an excessively long username string, typically exceeding the allocated buffer size in the server's memory allocation. The server processes this input without proper validation, leading to memory corruption that results in process termination or system instability. Organizations running OS2/Warp 4.5 systems should consider implementing network-level mitigations such as connection rate limiting and input filtering at the firewall level to prevent exploitation attempts. Additionally, the vulnerability highlights the importance of proper input validation and bounds checking in legacy systems, which were often not designed with modern security considerations in mind. The remediation approach should include applying vendor patches if available, or implementing network segmentation to isolate vulnerable FTP services, while also considering the replacement of legacy systems with more modern and secure alternatives that have proper input validation mechanisms and are regularly updated with security patches.