CVE-2026-85661 Details
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.
A vulnerability in Excel-MCP Server version 0.1.8 allows for arbitrary file read and write operations when the EXCEL_FILES_PATH environment variable is not set. This issue arises because the server fails to enforce proper path confinement in stdio mode, the default transport for desktop Model Context Protocol (MCP) clients. As a result, attackers can supply unchecked file paths to the server's read and write tools, accessing any file that the process can reach.
To address this vulnerability, path confinement should be enforced in stdio mode by requiring an explicitly configured base directory and validating every resolved path against it. Additionally, the formula denylist should be made case-insensitive to prevent bypasses.
Metrics
CVSS 4.0 Severity and Vector Strings:
VolerionCVSS 3.x Severity and Vector Strings:
No data available for CVSS Version 2.0 on this CVE.
Volerion
Assessed Sep 4, 2026CISA-ADP
Assessed Sep 14, 2026References to Advisories, Solutions, and Tools
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| URL | Source(s) | Tag(s) |
|---|---|---|
| https://github.com/haris-musa/excel-mcp-server | [email protected] | Vendor |
| https://github.com/haris-musa/excel-mcp-server/blob/v0.1.8/src/excel_mcp/server.py | [email protected] | Source CodeVendor |
| https://github.com/haris-musa/excel-mcp-server/blob/v0.1.8/src/excel_mcp/validation.py | [email protected] | Source CodeVendor |
| https://github.com/haris-musa/excel-mcp-server/issues/149 | [email protected] | ExploitIssue TrackingTechnical DescriptionVendor |
| https://www.vulncheck.com/advisories/excel-mcp-server-0.1.8-arbitrary-file-read-write-via-stdio-mode | [email protected] | Advisory |
Weakness Enumeration
| CWE-ID | CWE Name | Source |
|---|---|---|
| CWE-22 | Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal') | [email protected] |
Affected Products
| Product | Versions |
|---|---|
| excel-mcp-server | <= 0.1.8 (semver) |
CPE
Remediation
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Change History
2 change records found show changes
| Date | Action | Recorded By |
|---|---|---|
| Sep 14, 2026 | CVE Modified | CISA-ADP |
| Sep 4, 2026 | New CVE Received | [email protected] |