Vulnerability Description
excel-mcp-server is a Model Context Protocol server for Excel file manipulation. A path traversal vulnerability exists in excel-mcp-server versions up to and including 0.1.7. When running in SSE or Streamable-HTTP transport mode (the documented way to use this server remotely), an unauthenticated attacker on the network can read, write, and overwrite arbitrary files on the host filesystem by supplying crafted filepath arguments to any of the 25 exposed MCP tool handlers. The server is intended to confine file operations to a directory set by the EXCEL_FILES_PATH environment variable. The function responsible for enforcing this boundary — get_excel_path() — fails to do so due to two independent flaws: it passes absolute paths through without any check, and it joins relative paths without resolving or validating the result. Combined with zero authentication on the default network-facing transport and a default bind address of 0.0.0.0 (all interfaces), this allows trivial remote exploitation. This vulnerability is fixed in 0.1.8.
CVSS Score
CRITICAL
Related Weaknesses (CWE)
References
- https://github.com/haris-musa/excel-mcp-server/security/advisories/GHSA-j98m-w3x
- https://github.com/haris-musa/excel-mcp-server/security/advisories/GHSA-j98m-w3x
FAQ
What is CVE-2026-40576?
CVE-2026-40576 is a vulnerability with a CVSS score of 9.4 (CRITICAL). excel-mcp-server is a Model Context Protocol server for Excel file manipulation. A path traversal vulnerability exists in excel-mcp-server versions up to and including 0.1.7. When running in SSE or St...
How severe is CVE-2026-40576?
CVE-2026-40576 has been rated CRITICAL with a CVSS base score of 9.4/10. This is considered a critical vulnerability requiring immediate attention.
Is there a patch for CVE-2026-40576?
Check the references section above for vendor advisories and patch information. Review vendor security bulletins for remediation guidance.