---
title: "CVE-2026-40576: excel-mcp-server has a Path Traversal issue"
url: https://erroneo.us/security/cve/CVE-2026-40576/
description: "CVE-2026-40576 (excel-mcp-server (PyPI)): excel-mcp-server is a Model Context Protocol server for Excel file manipulation. A path traversal vulnerability…"
type: vulnerability-record
section: "Security Digest"
date_published: 2026-04-21
date_modified: 2026-04-24
publisher: erroneo.us
author: erroneo.us Security Desk
cve: "CVE-2026-40576"
kev: false
cvss: 9.4
epss: 0.00642
license: All rights reserved. Quote with attribution and a link.
---

# CVE-2026-40576: excel-mcp-server has a Path Traversal issue

**Signal:** Critical and remotely reachable. No known exploitation yet, but it is network-reachable without credentials. (Computed from CISA KEV, EPSS and CVSS; not an editorial verdict.)

## Should you act?

- Not in CISA KEV , but CISA’s SSVC assessment records a public proof-of-concept, so attack code exists.
- EPSS 0.6% , percentile 50: FIRST’s model estimates a 0.6% chance of exploitation activity in the next 30 days, higher than 50% of all scored CVEs (moderate). EPSS is a probability, not a verdict.
- Remotely reachable with no login and no user interaction. If the vulnerable service is exposed to the internet, prioritize it.
- Only applies if your dependency tree includes excel-mcp-server (PyPI) <= 0.1.7, fixed in 0.1.8 . Check your lockfile, including transitive dependencies.

## What it is

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 EXCELFILESPATH environment variable. The function responsible for enforcing this boundary — getexcelpath() — 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.

## Affected packages

- PyPI `excel-mcp-server` <= 0.1.7 → fixed: 0.1.8

## Affected products (CVE record)

- haris-musa excel-mcp-server: < 0.1.8

## Severity

- GitHub_M CVSS 3.1: 9.4 `CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:H/A:H`
- CISA-ADP CVSS 3.1: 9.4 `CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:H/A:H`
- GitHub CVSS 3.1: 9.4 `CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:H/A:H`

## Exploitation

- CISA KEV: not listed (no confirmed in-the-wild exploitation known to CISA).
- CISA SSVC assessment: exploitation poc , automatable yes , technical impact partial .
- FIRST EPSS (model of 2026-10-21): 0.64% probability of exploitation activity in the next 30 days; percentile 50.

## Sources

- [GitHub Advisory GHSA-j98m-w3xp-9f56](https://github.com/advisories/GHSA-j98m-w3xp-9f56)
- [CVE.org record CVE-2026-40576](https://www.cve.org/CVERecord?id=CVE-2026-40576)
- [NVD entry CVE-2026-40576](https://nvd.nist.gov/vuln/detail/CVE-2026-40576)
- [github.com](https://github.com/haris-musa/excel-mcp-server/security/advisories/GHSA-j98m-w3xp-9f56)
- [github.com](https://github.com/haris-musa/excel-mcp-server/commit/f51340ecd5778952405044b203d3a2d4c8a46833)

---
Source page: https://erroneo.us/security/cve/CVE-2026-40576/ · Security Digest: https://erroneo.us/security/ · More: https://erroneo.us/llms.txt