CVE-2026-40576: excel-mcp-server Path Traversal Allows Unauthenticated File Read and Overwrite (CVSS 9.4)
CVE-2026-40576 is a critical-severity path traversal issue (CVSS 9.4) in excel-mcp-server, a MCP server. Affected: excel-mcp-server <= 0.1.7 (fixed in 0.1.8). Fixed in 0.1.8.
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Key facts
- ID
CVE-2026-40576- Severity
- critical
- CVSS score
- 9.4
- Attack type
- Path traversal
- Component
- excel-mcp-server · MCP server
- Known exploited
- No known exploitation
- Published
- Last verified
What is CVE-2026-40576?
A path traversal flaw in excel-mcp-server let unauthenticated attackers read, write and overwrite arbitrary files. Its get_excel_path() passed absolute paths through without validation and failed to resolve ../ traversal sequences, and because the server binds to all network interfaces with no authentication by default, remote exploitation was straightforward. This is the recurring shape of MCP server risk: the code flaw is ordinary, but the default deployment posture turns it into remote file write.
Affected versions
| Affected | Fixed in |
|---|---|
excel-mcp-server <= 0.1.7 (fixed in 0.1.8) | 0.1.8 |
Am I affected by CVE-2026-40576?
You are affected if you run excel-mcp-server <= 0.1.7 (fixed in 0.1.8). Versions 0.1.8 and later include the fix.
How do I fix CVE-2026-40576?
Upgrade excel-mcp-server to 0.1.8+. Bind MCP servers to 127.0.0.1 rather than 0.0.0.0, put authentication in front of any MCP server reachable off-host, and run file-handling MCP servers against a scoped or read-only filesystem.
How do I find every machine running excel-mcp-server?
Anomity inventories the AI agents, MCP servers, IDE extensions and skills on each developer device, so you can see which machines run excel-mcp-server and which version, then enforce a policy on it.