CVE-2006-1253 in glFTPd
Summary
by MITRE
Unspecified vulnerability in glFTPd before 2.01 RC5 allows remote attackers to bypass IP checks via a crafted DNS hostname, possibly a hostname that appears to be an IP address.
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Analysis
by VulDB Data Team • 07/21/2018
The vulnerability identified as CVE-2006-1253 affects glFTPd versions prior to 2.01 RC5, representing a significant security flaw in the FTP server implementation that undermines fundamental network access controls. This unspecified vulnerability specifically targets the IP address validation mechanism within the glFTPd software, creating a potential pathway for remote attackers to circumvent established security boundaries. The flaw manifests when the system processes DNS hostnames that are crafted to appear as valid IP addresses, effectively allowing malicious actors to bypass the intended IP-based access restrictions that are typically enforced for security purposes.
The technical nature of this vulnerability stems from inadequate input validation and hostname resolution handling within the FTP daemon's authentication and access control modules. When glFTPd processes a DNS hostname for connection validation, it fails to properly distinguish between legitimate IP address representations and maliciously crafted hostnames that may contain embedded IP-like structures or other deceptive formatting. This weakness creates a condition where attackers can manipulate the hostname resolution process to present what appears to be a valid IP address while actually connecting from a different location or with different privileges. The vulnerability operates at the network layer where IP-based access controls are typically enforced, making it particularly dangerous as it undermines the fundamental security model that relies on IP address verification for access control decisions.
The operational impact of this vulnerability extends beyond simple access bypass, potentially enabling attackers to gain unauthorized access to FTP resources that should be restricted based on IP address criteria. Remote attackers can exploit this flaw to establish connections from locations that would normally be blocked or restricted, effectively circumventing network security policies that depend on IP address validation. This capability allows for unauthorized data access, potential data exfiltration, and could serve as a stepping stone for further attacks within the network infrastructure. The vulnerability particularly affects environments where glFTPd is used for sensitive data transfers and where IP-based access controls are implemented as part of the security architecture.
Security mitigations for this vulnerability require immediate patching of glFTPd installations to version 2.01 RC5 or later, which contains the necessary fixes for the hostname validation and IP address checking mechanisms. Organizations should also implement additional network-level controls such as firewall rules that restrict access to FTP services and monitor for suspicious hostname resolution patterns. The remediation process should include thorough testing of the updated software to ensure that the fix does not introduce compatibility issues with existing network configurations. Network administrators should also review and audit current IP-based access control policies to identify any potential exploitation that may have occurred prior to patching, while implementing more robust input validation measures across all network services that handle hostname and IP address resolution.
This vulnerability aligns with CWE-20, which addresses improper input validation, and represents a classic example of how DNS resolution handling can be exploited to bypass security controls. From an ATT&CK framework perspective, this vulnerability maps to techniques involving privilege escalation and initial access through service exploitation, as attackers can leverage the bypassed IP checks to gain access to restricted FTP resources. The flaw demonstrates the critical importance of proper input sanitization and validation in network services, particularly those that handle user authentication and access control decisions based on network address information. Organizations should consider implementing comprehensive logging and monitoring of FTP access attempts to detect potential exploitation attempts and establish baseline behaviors for normal network activity to identify anomalous patterns that may indicate successful exploitation of similar vulnerabilities.