Directory traversal vulnerability in Mike Spice My Calendar before 1.5 allows remote attackers to write arbitrary files via .. (dot dot) sequences in a URL.
Mike Spice My Calendar versions prior to 1.5 are vulnerable to a critical directory traversal attack, allowing attackers to write arbitrary files to the server. This vulnerability could lead to complete system compromise, including remote code execution and data exfiltration, by allowing attackers to overwrite critical system files or upload malicious web shells.
Step 1: Vulnerability Identification: The attacker identifies the vulnerable My Calendar application and its version (prior to 1.5).
Step 2: Payload Crafting: The attacker crafts a malicious URL containing a '..' sequence to navigate outside the intended directory. This URL typically includes a parameter that specifies a file path and the content to be written.
Step 3: Request Submission: The attacker sends the crafted URL to the vulnerable My Calendar application.
Step 4: Server-Side Processing: The application receives the request and processes the URL. Due to the lack of input validation, the '..' sequences are not filtered or neutralized.
Step 5: File Path Construction: The application constructs a file path based on the attacker-supplied input, including the '..' sequences, leading to a path outside the intended directory.
Step 6: File Write Operation: The application attempts to write the attacker-supplied content to the attacker-specified file path.
Step 7: Arbitrary File Write: The attacker's content is written to the specified location, potentially overwriting existing files or creating new ones. This could include uploading a web shell or other malicious code.
Step 8: System Compromise: If a web shell is uploaded, the attacker can then execute arbitrary commands on the server, leading to complete system compromise.
The vulnerability stems from a failure to properly sanitize user-supplied input used in file path construction. Specifically, the application does not validate or filter the use of '..' (dot-dot) sequences in the URL parameters used for file operations. This allows an attacker to craft a URL that, when processed by the application, constructs a file path outside of the intended directory. The lack of input validation allows the attacker to specify a target file path, and the application, without proper checks, writes the uploaded data to the attacker-specified location. This is a classic example of a path traversal vulnerability due to insufficient input validation. The root cause is a missing or inadequate implementation of secure file path handling and input sanitization.