Schema to Shell: The GraphQL-Ruby Introspection Nightmare

Amit Schendel

Senior Security Researcher

Jan 12, 2026·7 min read·8 visits

PoC Available

Executive Summary (TL;DR)

If your Ruby application loads GraphQL schemas from untrusted sources (like user uploads or external endpoints), you are likely vulnerable to RCE. The `graphql-ruby` gem was building code strings from schema names without validation. Update to the latest patch versions immediately.

A critical RCE in the popular `graphql-ruby` gem allows attackers to achieve remote code execution by providing malicious introspection data. By leveraging unsafe metaprogramming, specifically string-based `class_eval`, an attacker can inject arbitrary Ruby code during schema reconstruction.

Attack Flow Diagram

Official Patches

graphql-rubyOfficial Advisory and Patch Notes

GitLabGitLab Security Release 17.9.2

Fix Analysis (1)

Technical Appendix

CVSS Score

9.1/ 10

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H

EPSS Probability

5.86%

Top 10% most exploited

Affected Systems

graphql-ruby gem < 2.4.13GitLab < 17.9.2Applications using GraphQL::Client with untrusted endpointsAny Ruby app loading introspection data via `from_introspection`

Affected Versions Detail

Product	Affected Versions	Fixed Version
graphql-ruby Robert Mosolgo	< 2.4.13	2.4.13
graphql-ruby Robert Mosolgo	< 2.3.21	2.3.21
GitLab Community/Enterprise GitLab	17.7.0 - 17.7.6	17.7.7
GitLab Community/Enterprise GitLab	17.8.0 - 17.8.4	17.8.5

Attribute	Detail
CWE ID	CWE-94 (Code Injection)
CVSS v3.1	9.1 (Critical)
Attack Vector	Network (Introspection Loading)
EPSS Score	5.86% (High Probability)
Impact	Remote Code Execution (RCE)
Exploit Status	PoC Available