add unhandled error disclosure test

Author: nayanakto

MCP-Security/MCPUnhandledErrorDisclosureMalformedJson.yml

@@ -0,0 +1,63 @@
+---
+id: MCP_UNHANDLED_ERROR_DISCLOSURE_MALFORMED_JSONRPC
+info:
+  name: Unhandled Error Disclosure by Passing malformed JSON RPC payload
+  description: |
+    This test checks whether the MCP server discloses raw stack traces or internal error messages
+    (e.g., `SyntaxError`, `body-parser`, `raw-body`, `express` stack frames) directly to the MCP client.
+    Such disclosures may reveal sensitive implementation details that can be exploited for further attacks.
+  details: |
+    The test sends malformed JSON payloads to the MCP server.
+    If the response contains detailed stack traces, internal library names, or error messages,
+    it indicates that the MCP server does not sanitize error responses before returning them to clients.
+    Attackers can use this information to craft targeted exploits.
+  impact: |
+    Attackers gain knowledge of the underlying frameworks (`express`, `body-parser`, `raw-body`),
+    precise file paths, and error handling flaws.
+    This increases the risk of injection, DoS, or targeted exploitation of known vulnerabilities in exposed components.
+  category:
+    name: MCP
+    shortName: MCP
+    displayName: Model Context Protocol (MCP) Security
+  subCategory: MCP_UNHANDLED_ERROR_DISCLOSURE_MALFORMED_JSONRPC
+  severity: MEDIUM
+  tags:
+  - information_disclosure
+  - error_handling
+  - stack_trace
+  - mcp_security
+  references:
+  - https://owasp.org/www-community/Improper_Error_Handling
+  - https://cwe.mitre.org/data/definitions/209.html
+  - https://portswigger.net/kb/issues/00600400_server-errors
+  cwe:
+  - CWE-209
+  cve: []
+attributes:
+  nature: NON_INTRUSIVE
+  plan: PRO
+  duration: FAST
+api_selection_filters:
+  response_code:
+    gte: 200
+    lt: 300
+  method:
+    eq: POST
+  request_payload:
+    contains_all:
+    - method
+    - id
+    - jsonrpc
+    for_one:
+      extract: requestBody
+wordLists:
+  malformedPayload:
+  - "{"
+execute:
+  type: single
+  requests:
+  - req:
+      replace_body: "${malformedPayload}${requestBody}"
+validate:
+  response_payload:
+  - magic_validate: "Analyze the response to determine if it exposes stack traces, codebase file paths, dependency versions, underlying libraries, library-related errors, or any low-level system/debug errors not intended for external exposure. If none of these are present and the error is generic, do not flag as vulnerable."