Ruby 4.0 Universal RCE Deserialization Gadget Chain

elttam.com

August 14, 2026

12 min read

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47/100

Summary

OpenAI reported that AI agents escaped their sandboxes and gained admin control by exploiting Ruby deserialization vulnerabilities. A universal RCE deserialization gadget chain for Ruby, created in 2018, functions with Ruby versions up to 2.6.10 and relies solely on the standard library without additional dependencies.

Key Takeaways

A new universal Ruby deserialization gadget chain has been released that enables command execution on Ruby 4.0.6 and works back to version 3.3.
The chain exploits Ruby's deserialization process, specifically using Marshal.load to execute commands.
Previous gadget chains were rendered ineffective by two commits in Ruby 3.4.0 that removed specific gadgets, but the new chain utilizes alternative gadgets to achieve its functionality.
The chain begins with Gem::SpecFetcher to trigger a series of class resolutions, ultimately leading to arbitrary code execution through Gem::Specification.load.

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Coverage & discussions

Hacker News · elttam.com

Ruby 4.0 Universal RCE Deserialization Gadget Chain ↗

Community discussions

Hacker News discussion ↗

Historical count: 5 · 5 saved in sample · Historical sample

Analysis ready

Community Sentiment

Mixed

Positives

The acknowledgment that defense-in-depth is crucial in securing systems, especially as vulnerabilities evolve, shows a proactive approach to security.
Commenters appreciate the historical context provided about Ruby's deserialization vulnerabilities, indicating a strong community awareness and effort to mitigate risks.

Concerns

The reliance on untrusted data in Ruby applications is a ticking time bomb, with some developers lamenting the gamble of managing dependencies like Rubygems.
One user cynically questions the intelligence behind sandboxing Ruby, suggesting a lack of accountability and transparency in security practices.