CVE-2026-85661Public exploitNetwork attack vectorHinoki check available

Arbitrary file access via unconstrained stdio paths

Published Sep 4, 2026 · Updated Sep 4, 2026

Path traversal in Haris Musa Excel MCP Server 0.1.8 allows remote attackers to read or write arbitrary process-accessible files. In stdio mode, get_excel_path returns an attacker-supplied absolute path unchanged when EXCEL_FILES_PATH is unset, and file tools use that result without base-directory validation. Reachability requires control of an MCP filepath argument; reads expose workbook cell data, while writes can create or overwrite files the server process can access.

CVSS severity9.3
Critical
EPSS probability0.44%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkAvailable
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Summary

What happened

Path traversal in Haris Musa Excel MCP Server 0.1.8 allows remote attackers to read or write arbitrary process-accessible files. In stdio mode, get_excel_path returns an attacker-supplied absolute path unchanged when EXCEL_FILES_PATH is unset, and file tools use that result without base-directory validation. Reachability requires control of an MCP filepath argument; reads expose workbook cell data, while writes can create or overwrite files the server process can access.

The record

CVE
CVE-2026-85661
Published
Sep 4, 2026
Updated
Sep 4, 2026
Vendor
Haris Musa
Product
Excel MCP Server
Classifications
CWE-22, T1005, T1565.001
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Sep 4, 2026CVE publishedPublication date reported by the CVE source.
  2. Sep 4, 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 <=0.1.8

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Haris Musa · Excel MCP Serverversion=0 <=0.1.8

Published CVSS scores

9.3VulnCheck CNACVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
9.8VulnCheck CNACVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/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.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 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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