CVE-2026-40576Public exploitNetwork attack vector

Unauthenticated file read and overwrite via path traversal

Published Apr 21, 2026 · Updated Apr 21, 2026

Path traversal in Excel MCP Server before 0.1.8 allows remote attackers to read, write, or overwrite host files through MCP filepath arguments. The get_excel_path() function returns absolute paths unchanged and joins relative paths to EXCEL_FILES_PATH without resolving or checking containment. Exploitation requires reachable SSE or Streamable-HTTP mode; these transports add no authentication, and access is bounded by process permissions.

CVSS severity9.4
Critical
EPSS probability0.39%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Path traversal in Excel MCP Server before 0.1.8 allows remote attackers to read, write, or overwrite host files through MCP filepath arguments. The get_excel_path() function returns absolute paths unchanged and joins relative paths to EXCEL_FILES_PATH without resolving or checking containment. Exploitation requires reachable SSE or Streamable-HTTP mode; these transports add no authentication, and access is bounded by process permissions.

The record

CVE
CVE-2026-40576
Published
Apr 21, 2026
Updated
Apr 21, 2026
Vendor
Haris Musa
Product
Excel MCP Server
Classifications
CWE-22, T1005, T1565.001
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Apr 21, 2026CVE publishedPublication date reported by the CVE source.
  2. Apr 21, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=< 0.1.8

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Haris Musa · Excel MCP Serverversion=< 0.1.8

Published CVSS scores

9.4GitHub_MCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-22Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')
T1005Data from Local System
T1565.001Stored Data Manipulation

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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