CVE-2002-1628

Step 1: Payload Delivery: The attacker crafts a malicious HTTP request to vote.cgi, including a crafted type parameter. The type parameter is designed to contain .. sequences to traverse the directory structure. Step 2: Parameter Manipulation: The attacker sets the type parameter to a value like ../../../../etc/passwd or a path to a web shell file. Step 3: File Write: The vote.cgi script, due to the lack of input validation, uses the attacker-controlled type parameter to construct the file path. The script then attempts to write data (e.g., vote data or a malicious payload) to the specified path. Step 4: File Overwrite/Code Execution: If the attacker specifies a path to a critical system file (e.g., /etc/passwd) or a web shell file within the web server's document root, the attacker can overwrite the file. Overwriting /etc/passwd allows for user account creation and privilege escalation. Overwriting a web shell allows for arbitrary code execution.

The vulnerability stems from insufficient input validation within the vote.cgi script. Specifically, the script fails to properly sanitize the type parameter, which is used to determine the file path for writing vote data. By injecting .. (dot-dot) sequences into the type parameter, an attacker can manipulate the file path, escaping the intended directory and writing files to arbitrary locations on the server's filesystem. This lack of proper input validation allows for path traversal, leading to file overwrite and potential code execution. The root cause is a missing or inadequate check on the user-supplied input, allowing the attacker to control the file path. This is a classic example of a path traversal vulnerability.