pnpm v10+ Git Dependency Script Execution Bypass

Summary

A security bypass vulnerability in pnpm v10+ allows git-hosted dependencies to execute arbitrary code during pnpm install, circumventing the v10 security feature "Dependency lifecycle scripts execution disabled by default". While pnpm v10 blocks postinstall scripts via the onlyBuiltDependencies mechanism, git dependencies can still execute prepare, prepublish, and prepack scripts during the fetch phase, enabling remote code execution without user consent or approval.

Details

pnpm v10 introduced a security feature to disable dependency lifecycle scripts by default (PR #8897). This is implemented by setting onlyBuiltDependencies = [] when no build policy is configured:

File: pkg-manager/core/src/install/extendInstallOptions.ts (lines 290-291)

if (opts.neverBuiltDependencies == null && opts.onlyBuiltDependencies == null && opts.onlyBuiltDependenciesFile == null) {
  opts.onlyBuiltDependencies = []
}

This creates an allowlist that blocks all packages from running scripts during the BUILD phase in exec/build-modules/src/index.ts.

However, git-hosted dependencies are processed differently. During the FETCH phase, git packages are prepared using preparePackage():

File: exec/prepare-package/src/index.ts (lines 28-57)

export async function preparePackage (opts: PreparePackageOptions, gitRootDir: string, subDir: string) {
  // ...
  if (opts.ignoreScripts) return { shouldBeBuilt: true, pkgDir }  // Only checks ignoreScripts, not onlyBuiltDependencies

  const execOpts: RunLifecycleHookOptions = {
    // ...
    rawConfig: omit(['ignore-scripts'], opts.rawConfig),  // Explicitly removes ignore-scripts!
  }

  // Runs npm/pnpm install
  await runLifecycleHook(installScriptName, manifest, execOpts)

  // Runs prepare scripts
  for (const scriptName of PREPUBLISH_SCRIPTS) {  // ['prepublish', 'prepack', 'publish']
    await runLifecycleHook(newScriptName, manifest, execOpts)
  }
}

The ignoreScripts option defaults to false and is completely separate from onlyBuiltDependencies. The onlyBuiltDependencies allowlist is never consulted during the fetch phase.