Source: cve@mitre.org
TFTP is not running in a restricted directory, allowing a remote attacker to access sensitive information such as password files.
Remote attackers can leverage a misconfigured TFTP server to gain unauthorized access to sensitive files, including password databases, potentially leading to a complete system compromise. This vulnerability arises from the TFTP server's failure to restrict file access to a designated directory, enabling attackers to download arbitrary files from the system. Successful exploitation can result in data breaches and system takeover.
Step 1: Reconnaissance: The attacker identifies a target system running a TFTP server. This can be achieved through port scanning (e.g., using nmap to scan port 69/UDP).
Step 2: File Request: The attacker crafts a TFTP request to download a sensitive file. This often involves specifying the full path to the target file, such as /etc/passwd or /etc/shadow.
Step 3: Server Response: The TFTP server, due to its lack of directory restriction, processes the request and attempts to read the specified file.
Step 4: Data Transfer: The server transfers the contents of the requested file to the attacker.
Step 5: Credential Harvesting (if applicable): The attacker analyzes the downloaded file (e.g., /etc/passwd) to obtain user account information, including usernames and password hashes.
Step 6: Credential Cracking/Exploitation: The attacker uses the harvested credentials to attempt to gain unauthorized access to the system through methods like password cracking or brute-force attacks.
The vulnerability stems from a fundamental design flaw in many TFTP server implementations. The server, by default or through misconfiguration, does not properly restrict the file access to a specific, read-only directory. This allows a remote attacker to request any file on the system, including critical configuration files like /etc/passwd or shadow files containing password hashes. The root cause is the lack of input validation and path sanitization. The TFTP server accepts a filename from the client without verifying its location or preventing path traversal attempts (e.g., using ../ to navigate outside the intended directory). This allows an attacker to specify a path to a sensitive file, which the server then attempts to transfer. The absence of proper access controls and the trust placed in client-supplied filenames are the core weaknesses.
This vulnerability is a common attack vector for various threat actors. While specific APT groups are not directly linked to this CVE, it's a foundational technique used in broader attacks. This vulnerability could be leveraged by any attacker seeking initial access or privilege escalation. CISA KEV status: Not Listed (due to age and broad applicability, it's not specifically tracked in KEV, but the underlying issue is critical).
Monitor network traffic for TFTP requests (UDP port 69) and analyze the requested filenames. Look for requests targeting sensitive files like /etc/passwd, /etc/shadow, /etc/hosts, or configuration files.
Analyze TFTP server logs for suspicious activity, such as requests for files outside the expected directory or an unusually high volume of file transfer attempts.
Implement file integrity monitoring to detect unauthorized changes to critical system files.
Use intrusion detection systems (IDS) and intrusion prevention systems (IPS) with signatures that identify malicious TFTP requests.
Monitor for failed login attempts after a TFTP transfer, as this could indicate credential harvesting.
Disable TFTP if it is not required. This is the most effective mitigation.
If TFTP is required, configure the TFTP server to restrict file access to a specific, read-only directory (chroot).
Implement strong access controls on the TFTP server's root directory to prevent unauthorized file access.
Regularly audit and review TFTP server configurations to ensure they are secure.
Implement input validation and path sanitization to prevent path traversal attacks.
Use a firewall to restrict TFTP traffic to only trusted sources.
Keep the TFTP server software up-to-date with the latest security patches.
Consider using SFTP or SCP for secure file transfer instead of TFTP.