CVE-2010-2620 in Open-FTPD
Summary
by MITRE
Open&Compact FTP Server (Open-FTPD) 1.2 and earlier allows remote attackers to bypass authentication by sending (1) LIST, (2) RETR, (3) STOR, or other commands without performing the required login steps first.
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Analysis
by VulDB Data Team • 03/09/2017
The vulnerability identified as CVE-2010-2620 affects Open&Compact FTP Server version 1.2 and earlier, representing a critical authentication bypass flaw that fundamentally undermines the security model of the FTP service. This vulnerability resides in the server's handling of client commands and demonstrates a failure in proper session management and access control enforcement. The flaw specifically targets the authentication mechanism by allowing unauthorized access to server resources through direct command execution without proper login procedures. The affected commands LIST, RETR, and STOR are core FTP operations that typically require authenticated sessions to execute successfully, yet the vulnerability permits their execution in anonymous or unauthenticated contexts. This represents a fundamental breakdown in the server's security architecture where the expected sequence of operations is circumvented, allowing attackers to access file system resources without proper credentials.
The technical implementation of this vulnerability stems from improper validation of client command sequences within the FTP server's protocol handling logic. When clients send commands such as LIST to retrieve directory contents, RETR to retrieve files, or STOR to store files, the server should verify that an authentication process has been completed before granting access to these operations. However, the vulnerable implementation fails to enforce this prerequisite check, allowing command execution regardless of the client's authentication status. This flaw operates at the protocol level and affects the server's ability to maintain secure session boundaries, creating a persistent access vector that remains active throughout the server's operation. The vulnerability is particularly concerning because it affects multiple core FTP operations, providing attackers with broad access to file system resources without the need for additional exploitation techniques.
The operational impact of CVE-2010-2620 extends beyond simple unauthorized access to encompass complete compromise of the FTP server's file system. Attackers can leverage this vulnerability to enumerate directory structures, download sensitive files, upload malicious content, and potentially establish persistent access to the compromised system. The vulnerability creates a backdoor that remains active as long as the server is running, making it particularly dangerous for environments where FTP services are exposed to untrusted networks. Organizations using affected versions of Open-FTPD face significant risk of data breaches, system compromise, and potential lateral movement within their networks. The vulnerability also enables attackers to perform reconnaissance activities without detection, as the unauthorized access occurs through legitimate FTP protocol operations that may not trigger standard security monitoring alerts.
Mitigation strategies for this vulnerability require immediate patching of the affected Open&Compact FTP Server installations to version 1.3 or later, which includes proper authentication enforcement mechanisms. System administrators should implement network segmentation to limit exposure of FTP services to trusted networks only, while also deploying intrusion detection systems that monitor for unusual FTP command sequences. The vulnerability aligns with CWE-287, which addresses improper authentication issues, and represents a clear violation of the principle of least privilege that should govern all network services. From an ATT&CK framework perspective, this vulnerability maps to T1110.001 (Brute Force: Password Guessing) and T1078 (Valid Accounts) as attackers can leverage the bypass to gain access to legitimate accounts or operate under anonymous credentials. Additionally, organizations should conduct comprehensive security assessments of their FTP infrastructure, implement mandatory authentication for all operations, and establish proper logging and monitoring for FTP server activities to detect similar vulnerabilities or exploitation attempts.