CVE-2026-85661
Received Received - Intake

Path Traversal in excel-mcp-server via Unrestricted File Access

Publication date: 2026-09-04

Last updated on: 2026-09-04

Assigner: VulnCheck

Description
excel-mcp-server 0.1.8 fails to enforce path confinement in stdio mode when EXCEL_FILES_PATH is unset, allowing attackers to read and write arbitrary files. Attackers can supply unchecked file paths to read and write tools to access any file accessible to the process.

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Meta Information

Published
2026-09-04
Last Modified
2026-09-04
Generated
2026-09-04
AI Q&A
2026-09-04
EPSS Evaluated
N/A
NVD
CVE-2026-85661
EUVD
EUVD-2026-71117

Affected Vendors & Products

Showing 1 associated CPE
Vendor Product Version / Range
haris_musa excel_mcp_server to 0.1.8 (inc)

Helpful Resources

Exploitability

CWE
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KEV
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CWE ID Description
CWE-22 The product uses external input to construct a pathname that is intended to identify a file or directory that is located underneath a restricted parent directory, but the product does not properly neutralize special elements within the pathname that can cause the pathname to resolve to a location that is outside of the restricted directory.

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Executive Summary

CVE-2026-85661 is a path traversal vulnerability in excel-mcp-server version 0.1.8. When running in stdio mode without the EXCEL_FILES_PATH environment variable set, the server fails to restrict file access to a designated directory. Attackers can supply arbitrary file paths to read or write any file accessible to the process, bypassing intended security controls.

Detection Guidance

Check if excel-mcp-server version 0.1.8 is running in stdio mode without EXCEL_FILES_PATH set. Inspect server logs for unusual file path inputs or unauthorized access attempts. Test by supplying crafted file paths like '../etc/passwd' to see if files outside intended directories are accessible.

Impact Analysis

This vulnerability allows attackers to read sensitive files, write malicious files, or corrupt existing files on the system where excel-mcp-server is running. It could lead to data breaches, unauthorized file modifications, or execution of unsafe Excel functions via crafted inputs.

Compliance Impact

This vulnerability could lead to violations of GDPR (data protection) and HIPAA (health data privacy) by enabling unauthorized access to sensitive files. Organizations using this software may face compliance failures, legal penalties, and reputational damage due to data exposure or corruption.

Mitigation Strategies

Upgrade to a patched version of excel-mcp-server. If upgrading is not possible, ensure EXCEL_FILES_PATH is set to restrict file access. Disable stdio mode if not required. Implement input validation to sanitize file paths and enforce case-insensitive formula denylists.

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