CVE-2025-12562: GitLab GraphQL DoS Vulnerability

CVE-2025-12562 Overview

A denial of service vulnerability has been identified in GitLab Community Edition (CE) and Enterprise Edition (EE) affecting all versions from 11.10 before 18.4.6, 18.5 before 18.5.4, and 18.6 before 18.6.2. This vulnerability allows an unauthenticated user to create a denial of service condition by sending crafted GraphQL queries that bypass query complexity limits.

Critical Impact

Unauthenticated attackers can exhaust server resources and disrupt GitLab service availability by exploiting GraphQL query complexity bypass, potentially impacting critical DevOps workflows and CI/CD pipelines.

Affected Products

• GitLab Community Edition (CE) versions 11.10 to 18.4.5
• GitLab Enterprise Edition (EE) versions 11.10 to 18.4.5
• GitLab CE/EE versions 18.5.0 to 18.5.3
• GitLab CE/EE versions 18.6.0 to 18.6.1

Discovery Timeline

• 2025-12-10 - GitLab releases security patch 18.6.2
• 2025-12-11 - CVE-2025-12562 published to NVD
• 2025-12-23 - Last updated in NVD database

Technical Details for CVE-2025-12562

Vulnerability Analysis

This vulnerability is classified under CWE-770 (Allocation of Resources Without Limits or Throttling). The flaw exists within GitLab's GraphQL API implementation, where crafted queries can circumvent the built-in query complexity limits designed to prevent resource exhaustion. By exploiting this bypass, an attacker can submit queries that consume excessive server resources, leading to degraded performance or complete service unavailability.

The vulnerability is particularly concerning because it requires no authentication, meaning any network-accessible attacker can exploit it against publicly exposed GitLab instances. The attack targets the availability of the system without impacting confidentiality or integrity of data.

Root Cause

The root cause of this vulnerability lies in insufficient validation of GraphQL query complexity calculations. GitLab implements query complexity limits to prevent computationally expensive queries from overwhelming server resources. However, certain crafted query structures can bypass these complexity calculations, allowing deeply nested or resource-intensive queries to execute without triggering the protective limits.

This represents a failure in the resource allocation throttling mechanism, where specific query patterns were not properly accounted for in the complexity scoring algorithm, creating an avenue for denial of service attacks.

Attack Vector

The attack is network-based and requires no authentication or user interaction. An attacker can exploit this vulnerability by:

1. Identifying a publicly accessible GitLab instance with the GraphQL API enabled
2. Crafting malicious GraphQL queries designed to bypass complexity validation
3. Sending multiple crafted queries to exhaust server CPU, memory, or database connection resources
4. Causing service degradation or complete denial of service for legitimate users

The GraphQL API endpoint, typically accessible at /api/graphql, becomes the attack surface. Attackers can construct queries with specific structures that evade the complexity limits while still requiring substantial server-side processing. For detailed technical information about this vulnerability, refer to GitLab Issue #579152 and the associated HackerOne Report #3360710.

Detection Methods for CVE-2025-12562

Indicators of Compromise

• Unusual spikes in GraphQL API requests from single or distributed IP addresses
• Elevated CPU and memory utilization on GitLab application servers without corresponding legitimate user activity
• Slow response times or timeouts on GitLab web interface and API endpoints
• Database connection pool exhaustion or PostgreSQL performance degradation
• Log entries indicating abnormally complex or deeply nested GraphQL queries

Detection Strategies

• Monitor GraphQL endpoint (/api/graphql) request rates and implement anomaly detection for sudden traffic spikes
• Analyze query patterns in application logs for unusually deep nesting or repetitive field selections
• Configure alerting for resource utilization thresholds on GitLab servers (CPU > 90%, memory > 85%)
• Implement Web Application Firewall (WAF) rules to detect and block suspicious GraphQL query patterns

Monitoring Recommendations

• Enable detailed logging for the GitLab GraphQL API to capture query structures and execution times
• Deploy application performance monitoring (APM) tools to track query execution metrics
• Set up infrastructure monitoring for GitLab hosts to detect resource exhaustion patterns
• Review access logs regularly for patterns of unauthenticated GraphQL requests from suspicious sources

How to Mitigate CVE-2025-12562

Immediate Actions Required

• Upgrade GitLab to patched versions: 18.4.6, 18.5.4, or 18.6.2 immediately
• If immediate patching is not possible, consider temporarily restricting access to the GraphQL API
• Implement rate limiting on the /api/graphql endpoint at the load balancer or WAF level
• Monitor system resources closely for signs of ongoing exploitation attempts

Patch Information

GitLab has released security patches addressing this vulnerability in the following versions:

• GitLab 18.4.6 for the 18.4.x branch
• GitLab 18.5.4 for the 18.5.x branch
• GitLab 18.6.2 for the 18.6.x branch

Organizations should upgrade to the latest patched version appropriate for their deployment. Detailed patch information is available in the GitLab Patch Release 18.6.2 announcement.

Workarounds

• Implement rate limiting on GraphQL API endpoints using a reverse proxy or WAF to reduce the impact of exploitation attempts
• Restrict network access to the GitLab GraphQL API endpoint to trusted IP ranges if public access is not required
• Configure resource limits (CPU, memory) for GitLab processes using containerization or system-level controls to prevent complete service disruption
• Deploy a Web Application Firewall with rules to detect and block malicious GraphQL query patterns

# Example nginx rate limiting configuration for GitLab GraphQL endpoint
# Add to nginx configuration
limit_req_zone $binary_remote_addr zone=graphql_limit:10m rate=10r/s;

location /api/graphql {
    limit_req zone=graphql_limit burst=20 nodelay;
    limit_req_status 429;
    # existing proxy configuration
    proxy_pass http://gitlab-workhorse;
}