Source: cve@mitre.org
List of arbitrary files on Web host via nph-test-cgi script.
Critical vulnerability allows attackers to read arbitrary files on a web server by exploiting a flaw in the nph-test-cgi script. This can lead to sensitive information disclosure, including passwords, configuration files, and other confidential data, potentially enabling further attacks and complete system compromise.
Step 1: Identify the Vulnerable Script: The attacker identifies the presence of the nph-test-cgi script on the target web server, typically by scanning for common CGI script locations or through directory listing vulnerabilities.
Step 2: Craft the Malicious Request: The attacker constructs a URL that includes the nph-test-cgi script and a parameter specifying the target file to read (e.g., /nph-test-cgi?file=/etc/passwd).
Step 3: Submit the Request: The attacker sends the crafted URL to the web server.
Step 4: Script Execution and File Reading: The web server executes the nph-test-cgi script. The script, due to the lack of input validation, reads the contents of the specified file.
Step 5: Information Disclosure: The script returns the contents of the requested file (e.g., /etc/passwd) in the HTTP response, revealing sensitive information to the attacker.
The vulnerability stems from the insecure implementation of the nph-test-cgi script, a common CGI script used for testing web server functionality. The script likely lacks proper input validation and sanitization. Specifically, it allows attackers to specify a file path as a parameter, and the script then attempts to read and display the contents of that file. This lack of access control allows attackers to bypass intended restrictions and access any file the web server process has read permissions for. The root cause is a failure to implement input validation and access control on user-supplied parameters.
This vulnerability is not directly associated with specific APT groups or malware campaigns due to its age. However, the techniques used (e.g., arbitrary file read) are commonly employed in various attacks. This vulnerability could be a stepping stone for more sophisticated attacks. Not listed on CISA KEV due to its age and the specific script's obsolescence, but the underlying vulnerability type is relevant.
Monitor web server access logs for requests targeting nph-test-cgi or similar CGI scripts with suspicious parameters (e.g., file paths, directory traversal attempts).
Analyze HTTP response codes for unexpected results, such as the contents of system files (e.g., /etc/passwd, /etc/shadow) being returned.
Implement file integrity monitoring to detect unauthorized changes to critical system files.
Use a Web Application Firewall (WAF) to block requests containing suspicious patterns or file path manipulation attempts.
Network Intrusion Detection Systems (NIDS) can be configured to detect malicious requests based on signature-based or anomaly-based detection.
Remove the nph-test-cgi script or any other vulnerable CGI scripts from the web server. This is the most effective remediation.
If the script is necessary, thoroughly review and rewrite the script to implement robust input validation and sanitization. This includes validating the file path parameter to ensure it only allows access to intended files and directories.
Implement strict access control on the web server to restrict the permissions of the web server process. This limits the impact of a successful exploit.
Regularly update the web server software and all installed CGI scripts to patch any known vulnerabilities.
Implement a Web Application Firewall (WAF) to filter malicious requests.
Conduct regular vulnerability scans to identify and address potential weaknesses in the web application.