Details

Summary

When pnpm processes a package's directories.bin field, it uses path.join() without validating the result stays within the package root. A malicious npm package can specify "directories": {"bin": "../../../../tmp"} to escape the package directory, causing pnpm to chmod 755 files at arbitrary locations.

Note: Only affects Unix/Linux/macOS. Windows is not affected (fixBin gated by EXECUTABLE_SHEBANG_SUPPORTED).

Details

Vulnerable code in pkg-manager/package-bins/src/index.ts:15-21:

if (manifest.directories?.bin) {
  const binDir = path.join(pkgPath, manifest.directories.bin)  // NO VALIDATION
  const files = await findFiles(binDir)
  // ... files outside package returned, then chmod 755'd
}

The bin field IS protected with isSubdir() at line 53, but directories.bin lacks this check.

PoC

##### Create malicious package
mkdir /tmp/malicious-pkg
echo '{"name":"malicious","version":"1.0.0","directories":{"bin":"../../../../tmp/target"}}' > /tmp/malicious-pkg/package.json

##### Create sensitive file
mkdir -p /tmp/target
echo "secret" > /tmp/target/secret.sh
chmod 600 /tmp/target/secret.sh  # Private

##### Install
pnpm add file:/tmp/malicious-pkg

##### Check permissions
ls -la /tmp/target/secret.sh  # Now 755 (world-readable)

Impact

• Supply-chain attack via npm packages
• File permissions changed from 600 to 755 (world-readable)
• Affects non-dotfiles in predictable paths (dotfiles excluded by tinyglobby default)

Suggested Fix

Add isSubdir validation for directories.bin paths in pkg-manager/package-bins/src/index.ts, matching the existing validation in commandsFromBin():

if (manifest.directories?.bin) {
  const binDir = path.join(pkgPath, manifest.directories.bin)
  if (!isSubdir(pkgPath, binDir)) {
    return []  // Reject paths outside package
  }
  // ...
}

Severity

• CVSS Score: 6.7 / 10 (Medium)
• Vector String: CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:A/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N

References

• https://github.com/pnpm/pnpm/security/advisories/GHSA-v253-rj99-jwpq
• https://github.com/pnpm/pnpm/commit/17432ad5bbed5c2e77255ca6d56a1449bbcfd943
• https://github.com/pnpm/pnpm
• https://github.com/pnpm/pnpm/releases/tag/v10.28.2

This data is provided by OSV and the GitHub Advisory Database (CC-BY 4.0).

Details

Summary

When pnpm installs a file: (directory) or git: dependency, it follows symlinks and reads their target contents without constraining them to the package root. A malicious package containing a symlink to an absolute path (e.g., /etc/passwd, ~/.ssh/id_rsa) causes pnpm to copy that file's contents into node_modules, leaking local data.

Preconditions: Only affects file: and git: dependencies. Registry packages (npm) have symlinks stripped during publish and are NOT affected.

Details

The vulnerability exists in store/cafs/src/addFilesFromDir.ts. The code uses fs.statSync() and readFileSync() which follow symlinks by default:

const absolutePath = path.join(dirname, relativePath)
const stat = fs.statSync(absolutePath)  // Follows symlinks!
const buffer = fs.readFileSync(absolutePath)  // Reads symlink TARGET

There is no check that absolutePath resolves to a location inside the package directory.

PoC

##### Create malicious package
mkdir -p /tmp/evil && cd /tmp/evil
ln -s /etc/passwd leaked-passwd.txt
echo '{"name":"evil","version":"1.0.0","files":["*.txt"]}' > package.json

##### Victim installs
mkdir /tmp/victim && cd /tmp/victim
pnpm init && pnpm add file:../evil

##### Leaked!
cat node_modules/evil/leaked-passwd.txt

Impact

• Developers installing local/file dependencies
• CI/CD pipelines installing git dependencies
• Credential theft via symlinks to ~/.aws/credentials, ~/.npmrc, ~/.ssh/id_rsa

Suggested Fix

Use lstatSync to detect symlinks and reject those pointing outside the package root in store/cafs/src/addFilesFromDir.ts.

Severity

• CVSS Score: 6.7 / 10 (Medium)
• Vector String: CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:A/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N

References

• https://github.com/pnpm/pnpm/security/advisories/GHSA-m733-5w8f-5ggw
• https://github.com/pnpm/pnpm/commit/b277b45bc35ae77ca72d7634d144bbd58a48b70f
• https://github.com/pnpm/pnpm
• https://github.com/pnpm/pnpm/releases/tag/v10.28.2

This data is provided by OSV and the GitHub Advisory Database (CC-BY 4.0).

v10.28.2: pnpm 10.28.2

Compare Source

Patch Changes

• Security fix: prevent path traversal in directories.bin field.

• When pnpm installs a file: or git: dependency, it now validates that symlinks point within the package directory. Symlinks to paths outside the package root are skipped to prevent local data from being leaked into node_modules.

  This fixes a security issue where a malicious package could create symlinks to sensitive files (e.g., /etc/passwd, ~/.ssh/id_rsa) and have their contents copied when the package is installed.

  Note: This only affects file: and git: dependencies. Registry packages (npm) have symlinks stripped during publish and are not affected.

• Fixed optional dependencies to request full metadata from the registry to get the libc field, which is required for proper platform compatibility checks #​9950.

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