Introduction

Supply chain attacks have emerged as a critical threat in modern software development, exploiting trust in third-party dependencies, CI/CD pipelines, and package managers. These attacks can inject malicious code into widely used libraries, compromising thousands of projects before detection.

One of the most effective defenses is implementing cooldown phases for dependencies-delaying the installation of newly published packages until they have been available for a minimum period. This allows time for security reviews and reduces the risk of immediate compromise.

This article explains:

• What supply chain attacks are and how they work.
• How cooldown phases mitigate these risks.
• Practical steps to implement cooldowns across npm, pnpm, Bun, Yarn, pip, uv, and RubyGems.
• Additional strategies and tools to harden your supply chain security.

Understanding Supply Chain Attacks

Mechanisms and Vectors

Supply chain attacks target the trust relationships between software suppliers and consumers. Common attack vectors include:

Real-World Examples

Recent high-profile supply chain attacks include:

Cooldown Phases: A Critical Defense Mechanism

How Cooldowns Work

A cooldown phase delays the installation of newly released packages until they have been available for a minimum period (e.g., 7 days). This provides a window for:

• Security researchers to detect malicious packages.
• Automated tools to flag suspicious activity.
• Package maintainers to yank (remove) compromised versions.

Example Workflow:

1. A package version is published to a registry (e.g., npm, PyPI).
2. The package manager enforces a minimum release age (e.g., 7 days).
3. You hope that any malicious package will be detected and removed before it can be installed.

Effectiveness

• Most attacks are detected within hours of release.
• A 7-day cooldown would have blocked the majority of recent supply chain attacks (e.g., Bitwarden CLI, TanStack, Axios).
• Converts immediate risk into a human-manageable timeframe.

Implementing Cooldowns Across Package Managers

npm

Configuration:

• File: ~/.npmrc or project .npmrc
• Setting: min-release-age (in days)
• Example:

  min-release-age=7
  ignore-scripts=true

• Override (for trusted packages):

  npm install <package> --min-release-age 0

pnpm

Configuration:

• File: ~/.config/pnpm/rc or pnpm-workspace.yaml
• Setting: minimum-release-age (in minutes)
• Example:

minimum-release-age: 10080 # 7 days
minimum-release-age-exclude:
  - "@trusted/*"

• Override:

  pnpm add <package> --minimum-release-age 0

• Default: Since pnpm v11, the default cooldown is 1 day (1440 minutes).

Additional Security Features:

• block-exotic-subdeps=true (blocks dependencies not in the lockfile).
• trust-policy=low (restricts untrusted registries).

Source: pnpm Supply Chain Security

Bun

Configuration:

• File: ~/.bunfig.toml
• Setting: minimumReleaseAge (in seconds)
• Example:

  [install]
  minimumReleaseAge = 604800  # 7 days

• Override:

  bun add <package> --minimum-release-age 0

Yarn

Configuration:

• File: .yarnrc.yml
• Setting: npmMinimalAgeGate (in minutes)
• Example:

npmMinimalAgeGate: 10080 # 7 days
npmPreapprovedPackages:
  - typescript
  - eslint

• Override: Not directly supported (use resolutions or version constraints).

Python (uv and pip)

uv

• Command-line flag:

  uv pip install --exclude-newer "7 days"

• Override:

  uv pip install --exclude-newer "0 days"

pip

• Absolute timestamp (older pip versions):

  pip install --uploaded-prior-to 2026-05-13

• Relative duration (pip 26.1+):

  pip install --uploaded-prior-to "7 days"

• Override:

  pip install --uploaded-prior-to "0 days"

Source: pip Documentation

RubyGems

• Native Support: None (as of May 2026).
• Community Solution:
  • Use gem.coop (a registry that enforces a 48-hour cooldown for Bundler users).
  • Configure Bundler to use gem.coop:

    source "https://gem.coop"

Broader Strategies for Preventing Supply Chain Attacks

Tools and Services to Enhance Supply Chain Security

Comparative Table of Cooldown Configurations

Conclusion

Supply chain attacks are a growing and severe threat to software development, but cooldown phases provide a simple yet powerful defense. By delaying the installation of newly released packages, developers gain critical time to detect and mitigate malicious releases.

Key Takeaways

1. Implement cooldowns in your package managers (npm, pnpm, Bun, Yarn, pip, uv, RubyGems).
2. Combine cooldowns with other security measures:
   • Verify package integrity (signatures, checksums).
   • Audit dependencies regularly.
   • Pin versions and commit lockfiles.
   • Secure CI/CD pipelines.
   • Adopt zero-trust principles.
3. Use automation tools like DepsGuard, StepSecurity, and OpenRewrite to enforce cooldowns and audit configurations.
4. Stay informed about supply chain threats and best practices (e.g., cooldowns.dev).

Call to Action

• Start today: Add a 7-day cooldown to your projects.
• Educate your team: Share this guide and discuss supply chain risks.
• Contribute: Report malicious packages and support open-source security initiatives.

By adopting these practices, you can significantly reduce the risk of supply chain compromises and build more secure software.

References

• Cooldowns.dev
• pnpm Supply Chain Security
• DepsGuard
• StepSecurity
• OpenRewrite
• GitHub Supply Chain Security