A critical path traversal vulnerability in excel-mcp-server allows unauthenticated attackers to read or write arbitrary files on the host system.

This is a path traversal vulnerability (CWE-22) occurring because the server fails to validate file paths when the EXCEL_FILES_PATH environment variable is not configured. An unauthenticated attacker can supply malicious file paths to the server tools to bypass intended directory restrictions.

The ability to read and write arbitrary files on the host system represents a complete compromise of the server environment. An attacker could exfiltrate sensitive configuration files, inject malicious scripts into system directories, or overwrite critical binaries to achieve persistent code execution. Given the CVSS score of 9.8, this vulnerability poses an extreme risk to data confidentiality, integrity, and system availability.

Immediate Action: Ensure the EXCEL_FILES_PATH environment variable is explicitly set to a restricted, dedicated directory for all deployments. While a specific patch version is not currently identified in the provided data, users should monitor the project repository for an official update that enforces path confinement by default.

Proactive Monitoring: Review application and system access logs for any file operations involving unexpected directory paths or attempts to access configuration files outside the expected data storage folder.

Compensating Controls: If immediate patching is not possible, deploy the application within a containerized environment with strictly limited filesystem permissions, ensuring the process user cannot access files outside the designated Excel data directory.

Public Exploit Available: Unknown

This vulnerability is critical due to the lack of input validation for file operations. Administrators must immediately configure the EXCEL_FILES_PATH environment variable to restrict the scope of file access to a safe, isolated directory. Continuous monitoring of file system activity is required until a vendor-supplied patch is applied to enforce these restrictions programmatically.