CVE-2026-40576: excel-mcp-server Path Traversal (CWE-22) Enables Remote File Read and Write
excel-mcp-server, a Model Context Protocol server for Excel files, has a path traversal flaw (CWE-22) in versions up to and including 0.1.7 when used over SSE or Streamable-HTTP transport. The record states that an unauthenticated network attacker could read, write and overwrite arbitrary files on the host, and that the issue is fixed in 0.1.8. The record reports a CVSS 3.1 base score of 9.4, and CISA KEV does not list this CVE.
Overview
excel-mcp-server is a Model Context Protocol server for Excel file manipulation. The record describes a path traversal weakness (CWE-22) in how file paths are handled. It affects versions up to and including 0.1.7 and is fixed in 0.1.8. See the GitHub security advisory GHSA-j98m-w3xp-9f56.
Impact
- According to the record, an unauthenticated attacker on the network could read, write and overwrite arbitrary files on the host when the server runs in SSE or Streamable-HTTP mode.
- The record gives a CVSS 3.1 base score of 9.4 (Critical), with low confidentiality impact and high integrity and availability impact.
- The record describes two independent flaws in get_excel_path(): absolute paths pass through without checks, and relative paths are joined without resolving or validating the result.
- The record notes that the default transport has no authentication and that the default bind address is 0.0.0.0, which increases exposure.
Affected products and versions
- Product: excel-mcp-server.
- Affected: versions up to and including 0.1.7, according to the record description.
- Fixed: version 0.1.8, according to the record description.
- The structured affected and fixes lists in the record are empty, so exact package ranges should be confirmed in the advisory.
Exploitation status
The record shows that this CVE is not listed in the CISA KEV catalog. No confirmed exploitation in the wild appears in the sources consulted for this analysis. The record also includes an EPSS probability of 0.00642 and a percentile of 0.49407.
Remediation and mitigation
- Upgrade to version 0.1.8 or later, which the record identifies as the fixed version.
- Until the upgrade is complete, do not expose the SSE or Streamable-HTTP transports to untrusted networks. Restrict access with network controls and keep the service behind access controls that operate outside the server.
- Change the default bind address to a loopback or a specific internal interface where remote access is not needed.
- Run the process under a dedicated low-privilege account, and limit its file system permissions to the intended Excel working directory.
Detection guidance
- Review server logs and network access to the MCP endpoint for requests from unexpected sources or at unusual times.
- Monitor for unexpected creation or modification of files outside the designated EXCEL_FILES_PATH directory.
- Inventory deployments to identify instances that run versions up to 0.1.7.
Limitations of the available information
- The record does not include structured affected or fixed version data, so the exact range depends on the advisory.
- The record shows a source status of Deferred, and the NVD analysis may change.
- The EPSS date in the record (2026-10-13) is later than the publication date (2026-04-21). Treat the EPSS values as unverified until confirmed.
Frequently asked questions
Which versions are affected?
The record describes versions up to and including 0.1.7 as affected. The record states that the issue is fixed in 0.1.8.
Is this CVE known to be exploited in the wild?
The record does not list this CVE in CISA KEV, and no confirmed exploitation in the wild appears in the sources consulted.
Does the transport mode matter?
Yes. The record describes the SSE and Streamable-HTTP transports as the documented remote modes, and says the default transport has no authentication and binds to 0.0.0.0.
This analysis was drafted with AI assistance from verified source data and automatically checked against it.