CVE-2001-1501 in ProFTPD
Summary
by MITRE
The glob functionality in ProFTPD 1.2.1, and possibly other versions allows remote attackers to cause a denial of service (CPU and memory consumption) via commands with large numbers of wildcard and other special characters, as demonstrated using an ls command with multiple (1) "*/..", (2) "*/.*", or (3) ".*./*?/" sequences in the argument.
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Analysis
by VulDB Data Team • 09/24/2025
The vulnerability identified as CVE-2001-1501 represents a critical denial of service weakness in the ProFTPD 1.2.1 server implementation that stems from inadequate handling of glob pattern processing. This flaw specifically targets the file listing functionality where the server processes wildcard characters and special sequences during command execution. The vulnerability manifests when remote attackers craft malicious commands containing excessive wildcard patterns that cause the ProFTPD server to consume disproportionate computational resources during pattern expansion. The attack vector exploits the server's glob expansion algorithm which fails to implement proper bounds checking or resource limiting mechanisms when processing complex wildcard expressions.
The technical implementation of this vulnerability lies in the server's insufficient input validation and resource management during glob pattern processing. When the ls command receives arguments containing sequences such as "/..", "/.", or "../*?/", the ProFTPD server attempts to expand these patterns through recursive directory traversal and pattern matching operations. The algorithmic complexity of these operations grows exponentially with the number of wildcard characters, leading to massive CPU utilization and memory consumption. This behavior directly violates the principle of resource exhaustion protection as outlined in CWE-400, where insufficient resource management allows attackers to consume system resources and potentially crash the service.
The operational impact of this vulnerability extends beyond simple service disruption to create significant system stability concerns for affected organizations. When exploited, the vulnerability causes the ProFTPD daemon to consume 100% CPU cycles and rapidly deplete available memory resources, effectively rendering the FTP service unavailable to legitimate users. This type of attack falls under the ATT&CK technique T1499.004 for Network Denial of Service, where adversaries leverage protocol-specific weaknesses to exhaust system resources. The vulnerability affects not only the immediate availability of the FTP service but can also impact other services running on the same system due to resource starvation, creating cascading failures in network infrastructure.
Mitigation strategies for CVE-2001-1501 should focus on both immediate patching and defensive configuration measures. Organizations must upgrade to ProFTPD versions that address this vulnerability, typically those beyond 1.2.1, as the original implementation contained fundamental flaws in pattern processing logic. Additionally, implementing rate limiting and command execution timeouts can provide defense-in-depth protection against similar attacks. Network-level controls such as firewall rules that restrict FTP command execution or implement connection rate limiting can help prevent exploitation. The vulnerability demonstrates the importance of implementing proper input sanitization and resource consumption limits as recommended by CWE-129 and CWE-131, which address issues related to improper bounds checking and resource management in protocol implementations. Regular security auditing of network services and implementing automated monitoring for unusual CPU and memory consumption patterns can help detect exploitation attempts before they cause significant service disruption.