CVE-1999-0183 in Linux
Summary
by MITRE
linux implementations of tftp would allow access to files outside the restricted directory.
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Analysis
by VulDB Data Team • 10/26/2025
The vulnerability described in CVE-1999-0183 represents a critical directory traversal flaw affecting linux implementations of the trivial file transfer protocol tftp server. This security weakness stems from inadequate input validation and path handling within tftp server implementations, allowing remote attackers to access files outside the designated restricted directory structure. The flaw specifically impacts tftp servers that fail to properly sanitize user-supplied filenames or paths, creating opportunities for unauthorized file system access.
The technical nature of this vulnerability aligns with common weakness enumerations such as CWE-22, which describes improper limitation of a pathname to a restricted directory, also known as path traversal or directory traversal attacks. The flaw operates by exploiting how tftp servers process file requests that contain directory traversal sequences such as "../" or similar path manipulation techniques. When a client requests a file using these sequences, the vulnerable tftp server fails to properly validate or canonicalize the requested path, allowing access to files located outside the intended serving directory.
From an operational perspective, this vulnerability presents significant security implications for systems running tftp servers in network environments. Attackers could potentially access sensitive system files, configuration data, or other restricted resources that should remain isolated from unauthorized access. The impact extends beyond simple data exposure to include potential system compromise through access to critical system files, logs, or configuration parameters that could aid in further attacks. This vulnerability particularly affects network infrastructure devices that rely on tftp for firmware updates or configuration management, where unauthorized access to system files could lead to complete system compromise.
The attack surface for this vulnerability includes any linux system running a tftp server implementation that does not properly validate file paths, typically those used for network booting, firmware distribution, or remote configuration management. Systems with default tftp server configurations that do not restrict file access to specific directories become vulnerable to exploitation. The vulnerability is particularly concerning in environments where tftp servers are used for booting network devices or distributing firmware updates, as these scenarios often involve systems with elevated privileges or access to sensitive network infrastructure components.
Mitigation strategies for this vulnerability should focus on implementing proper input validation and path canonicalization within tftp server implementations. System administrators should ensure that tftp servers are configured to operate within strict directory boundaries and that all file requests are properly validated before processing. The implementation of access control lists and proper file system permissions can help prevent unauthorized access to restricted directories. Additionally, organizations should consider migrating to more secure protocols such as ftps or sftp for file transfers where possible, as these protocols provide better security controls and authentication mechanisms. Regular security audits and vulnerability assessments should be conducted to identify and remediate similar path traversal vulnerabilities in other network services and applications. The remediation process should include updating to patched versions of tftp server implementations and implementing network segmentation to limit access to tftp services to authorized users and systems only.