Critical severity · published Sep 4, 2026
CVE-2026-85661
excel-mcp-server 0.1.8 Arbitrary File Read/Write via stdio mode
9.8
CVSS
0.7%
EPSS
No
On KEV
Description
excel-mcp-server 0.1.8 fails to enforce path confinement in stdio mode when EXCEL_FILES_PATH is unset, allowing attackers to read and write arbitrary files. Attackers can supply unchecked file paths to read and write tools to access any file accessible to the process.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Confidentiality
High
Integrity
High
Availability
High
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.7% · higher than 53% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
EX
excel-mcp-server · haris-musa
through 0.1.8 · source: vendor
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-85661
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-85661
github.com
https://github.com/haris-musa/excel-mcp-server
github.com
https://github.com/haris-musa/excel-mcp-server/blob/v0.1.8/src/excel_mcp/server.py
github.com
https://github.com/haris-musa/excel-mcp-server/blob/v0.1.8/src/excel_mcp/validation.py
github.com
https://github.com/haris-musa/excel-mcp-server/issues/149
www.vulncheck.com
https://www.vulncheck.com/advisories/excel-mcp-server-0.1.8-arbitrary-file-read-write-via-stdio-mode
More from excel-mcp-server
9.4
CVE-2026-40576
Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal') in excel-mcp-server