CVE-2025-27407: graphql-ruby RCE Vulnerability

CVE-2025-27407 Overview

CVE-2025-27407 is a critical Remote Code Execution (RCE) vulnerability in graphql-ruby, a popular Ruby implementation of GraphQL. The vulnerability exists in the schema loading functionality, specifically in GraphQL::Schema.from_introspection and GraphQL::Schema::Loader.load methods. When a malicious schema definition is loaded from an untrusted source, attackers can achieve arbitrary code execution on the target system.

This vulnerability is particularly dangerous for applications that dynamically load GraphQL schemas from external sources, including those using GraphQL::Client to fetch schemas via GraphQL introspection. The attack can be executed over the network without authentication, making it a significant supply chain security risk.

Critical Impact

Remote code execution through malicious GraphQL schema injection allows attackers to fully compromise systems that load untrusted schema definitions, potentially leading to complete system takeover.

Affected Products

• graphql-ruby versions 1.11.5 through 1.11.7
• graphql-ruby versions 1.12.0 through 1.12.24
• graphql-ruby versions 1.13.0 through 1.13.23
• graphql-ruby versions 2.0.0 through 2.0.31
• graphql-ruby versions 2.1.0 through 2.1.13
• graphql-ruby versions 2.2.0 through 2.2.16
• graphql-ruby versions 2.3.0 through 2.3.20
• GitLab versions prior to 17.9.2

Discovery Timeline

• 2025-03-12 - CVE-2025-27407 published to NVD
• 2025-11-03 - Last updated in NVD database

Technical Details for CVE-2025-27407

Vulnerability Analysis

This vulnerability is classified as CWE-94 (Improper Control of Generation of Code), commonly known as Code Injection. The flaw resides in how graphql-ruby processes schema definitions during the introspection loading phase. When an application uses GraphQL::Schema.from_introspection or the underlying GraphQL::Schema::Loader.load method to parse and instantiate a GraphQL schema from JSON data, maliciously crafted input can trigger arbitrary Ruby code execution.

The vulnerability is exploitable over the network without requiring any privileges or user interaction. The scope of the vulnerability extends beyond the vulnerable component, meaning a successful exploit can affect resources beyond the immediate graphql-ruby library, potentially compromising the entire hosting system.

Applications at highest risk are those that:

• Fetch GraphQL schemas from remote or external APIs
• Use GraphQL::Client to perform schema introspection against untrusted endpoints
• Process user-supplied or third-party schema definitions
• Implement federated GraphQL architectures that merge external schemas

Root Cause

The root cause lies in the schema loader's insufficient validation of incoming schema definition data. When processing introspection results, the loader fails to properly sanitize or restrict certain schema elements that can be manipulated to inject executable Ruby code. This allows attackers to craft a malicious schema definition that, when parsed, executes arbitrary code within the Ruby interpreter context.

The vulnerability was introduced in version 1.11.5 and persisted across multiple major version branches until the coordinated patch release.

Attack Vector

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

1. Setting up a malicious GraphQL endpoint that returns a crafted introspection response
2. Waiting for a vulnerable application to perform schema introspection against the malicious endpoint
3. The malicious schema definition triggers code execution during the loading process

Alternatively, if an application accepts schema definitions from untrusted sources (files, APIs, user input), the attacker can directly supply the malicious payload.

The vulnerability allows attackers to achieve complete system compromise with the ability to exfiltrate sensitive data, install backdoors, move laterally within the network, or cause denial of service. For detailed technical information, see the GitHub Security Advisory GHSA-q92j-grw3-h492.

Detection Methods for CVE-2025-27407

Indicators of Compromise

• Unexpected outbound network connections from Ruby application processes
• Unusual process spawning from Ruby or Rails application workers
• Anomalous file system modifications in application directories
• Suspicious GraphQL introspection requests to or from unknown endpoints
• Unexpected system command execution traced back to graphql-ruby gem loading

Detection Strategies

• Monitor application logs for schema loading operations from external sources
• Implement network monitoring to detect connections to unknown GraphQL endpoints
• Use runtime application self-protection (RASP) to detect code injection attempts
• Audit gem dependencies using bundle audit or similar tools to identify vulnerable versions

Monitoring Recommendations

• Enable verbose logging for GraphQL schema loading operations in non-production environments
• Implement alerting for any GraphQL::Schema.from_introspection calls with external data
• Monitor Ruby process behavior for signs of post-exploitation activities
• Track network traffic patterns to identify unauthorized schema fetching operations

How to Mitigate CVE-2025-27407

Immediate Actions Required

• Upgrade graphql-ruby to a patched version immediately: 1.11.8, 1.12.25, 1.13.24, 2.0.32, 2.1.14, 2.2.17, or 2.3.21
• Audit all code paths that call GraphQL::Schema.from_introspection or GraphQL::Schema::Loader.load
• If using GitLab, upgrade to version 17.9.2 or later
• Review and validate all external GraphQL schema sources in your application

Patch Information

Multiple patched versions have been released to address this vulnerability across all affected version branches:

For additional vendor information, see the GitLab Patch Release 17.9.2 and Debian LTS Announcement.

Workarounds

• Avoid loading GraphQL schemas from untrusted or external sources until patching is complete
• Implement strict allowlisting for any GraphQL endpoints used for schema introspection
• Consider using static schema definitions instead of dynamic introspection loading
• Add network-level restrictions to prevent applications from connecting to unauthorized GraphQL endpoints

# Update graphql-ruby to patched version
bundle update graphql

# Verify the installed version is patched
bundle show graphql

# Run security audit to confirm fix
bundle audit check --update