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tech 5 June 2026

Cooldown Support for Ruby Bundler: Securing Your Dependencies

Learn how cooldown support in Ruby Bundler enhances your project's security by delaying the installation of new gem versions until they are vetted.

Article inspired by the original source
Cooldown Support for Ruby Bundler ↗ blog.rubygems.org

Introduction: Securing Your Dependencies with Bundler

In a world where software supply chain security is paramount, Ruby Bundler 4.0.13 introduces an innovative feature: cooldown support. This feature delays the installation of new gem versions, providing a crucial vetting window to prevent malicious releases. Let's delve into how it works and how to implement it in your projects.

Why is Cooldown Necessary?

Supply chain attacks are increasingly common, and RubyGems is not immune. Most attacks exploit a narrow time window after an account has been compromised and a malicious version has been published. This is where cooldown comes in, refusing to resolve dependencies to versions too new to be safe.

Facts and Figures

According to a Sonatype study, supply chain attacks increased by 650% between 2020 and 2021. Bundler's cooldown aims to mitigate this vulnerability by introducing a validation delay.

How Cooldown Works

Cooldown uses a time-based filter leveraging the created_at timestamp provided by rubygems.org's v2 compact index. Versions that cannot prove their age, such as those from older gem servers or private registries, are treated as outside the window and remain resolvable.

Implementation

To activate cooldown, simply update Bundler to version 4.0.13 and set a delay in the Gemfile:

``ruby source "https://rubygems.org", cooldown: 7 gem "rails" gem "puma" ``

This ensures that every developer and CI run enforces the same vetting window without extra setup.

Advanced Options

Cooldown can be configured more granularly, per project, globally, or via the environment. Here are some useful commands:

  • Per project: $ bundle config set cooldown 7
  • Globally: $ bundle config set --global cooldown 7
  • Via the environment: $ BUNDLE_COOLDOWN=7 bundle install

Benefits of the Cooldown Approach

By delaying the installation of new versions, cooldown allows developers to benefit from the added security of a community that has had time to vet new releases. This complements other security measures like mandatory two-factor authentication.

Conclusion

Ruby Bundler's cooldown support is a significant advancement in bolstering the security of your Ruby projects. By delaying the installation of new gem versions, it provides an extra layer of protection against supply chain attacks.

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Ruby Bundler Cooldown Supply Chain Security RubyGems Dependency Management
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