Attack Chain

1. The attacker identifies a vulnerable instance of filesystem-mcp-server version 1.0.0 exposed to the network.
2. The attacker crafts a malicious request targeting the read_file_tool or write_file_tool component.
3. The crafted request includes a path traversal sequence (e.g., ../) within the file path parameter.
4. The is_path_allowed function fails to properly sanitize the input path, allowing the traversal sequence to bypass intended restrictions.
5. The application processes the request, accessing a file outside the intended directory.
6. If using read_file_tool, the contents of the unauthorized file are returned to the attacker.
7. If using write_file_tool, the attacker can overwrite legitimate files, potentially injecting malicious code.
8. Successful exploitation allows the attacker to read sensitive information or achieve arbitrary code execution on the server.

Impact

Successful exploitation of this path traversal vulnerability (CVE-2026-7400) can allow an attacker to read arbitrary files from the affected server, potentially exposing sensitive data such as configuration files, credentials, or internal documents. If the write_file_tool is exploited, the attacker might overwrite critical system files, leading to denial of service or arbitrary code execution. This issue affects systems running geekgod382 filesystem-mcp-server version 1.0.0.

Recommendation

• Upgrade to geekgod382 filesystem-mcp-server version 1.1.0 to apply the patch (45364545fc60dc80aadcd4379f08042d3d3d292e) that fixes CVE-2026-7400.
• Deploy the Sigma rule “filesystem-mcp-server Path Traversal Attempt” to detect potential exploitation attempts against the filesystem-mcp-server.
• Monitor web server logs for suspicious requests containing path traversal sequences (../, ..\\) targeting file access endpoints, as this may indicate exploitation attempts.
• Implement input validation and sanitization measures to prevent path traversal attacks, even after upgrading, as defense-in-depth.