Security Digest · Vulnerability record
CVE-2026-40576: excel-mcp-server has a Path Traversal issue
excel-mcp-server is a Model Context Protocol server for Excel file manipulation.
CVSS 9.4 Critical EPSS 0.6% · p50
Should you act?
Critical and remotely reachable
No known exploitation yet, but it is network-reachable without credentials. This signal is computed from CISA KEV, EPSS and CVSS data; it is not an editorial verdict.
- 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.
From the GitHub advisory
Summary
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.
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Details
Weakness type: CWE-22.
Product: excel-mcp-server (PyPI) · Assigned by: GitHub_M · Published: 2026-04-21
Affected and fixed versions
| Ecosystem | Package | Vulnerable | First fixed |
|---|---|---|---|
| PyPI | excel-mcp-server | <= 0.1.7 | 0.1.8 |
| Vendor | Product | Affected versions (per CVE record) |
|---|---|---|
| haris-musa | excel-mcp-server | < 0.1.8 |
Severity scores
| Scored by | CVSS | Score | Vector |
|---|---|---|---|
| GitHub_M | 3.1 | 9.4 Critical | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:H/A:H |
| CISA-ADP | 3.1 | 9.4 Critical | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:H/A:H |
| GitHub | 3.1 | 9.4 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:H/A:H |
- Attack vector: network (remotely reachable)
- Attack complexity: low
- Privileges required: none (no login)
- User interaction: none
- Scope: unchanged
CVSS measures how bad a flaw is if exploited, not how likely exploitation is. Read it next to the exploitation data below.
Exploitation and urgency
- 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.
Timeline
- — GitHub-reviewed advisory GHSA-j98m-w3xp-9f56 published (critical)
- — CVE record last updated
- — CVE record published by GitHub_M
Sources and references
Original sources first. Version and fix details should always be confirmed against the vendor or project advisory.
Vulnerability records
- GitHub Advisory GHSA-j98m-w3xp-9f56 github.com
- CVE.org record CVE-2026-40576 cve.org
- NVD entry CVE-2026-40576 nvd.nist.gov
Other references from the CVE record and advisory
- github.com github.com
- github.com github.com