CVE-2026-50021
pnpm Has an Integrity Check Bypass via Missing Lockfile Integrity Field
Description
## Summary pnpm's tarball extraction worker skips integrity verification when the `integrity` field is absent from the lockfile resolution. If an attacker can both modify `pnpm-lock.yaml` to remove the `integrity:` field and cause the referenced registry URL to serve altered package content, `pnpm install --frozen-lockfile` can install the altered package without an integrity error. npm's `npm ci` enforces integrity by default; pnpm's behavior of silently skipping verification is a pnpm-specific fail-open gap. ## Vulnerability Details The `addTarballToStore` function in `worker/src/start.ts` (lines 189-204) checks `if (integrity)` before verifying the tarball hash. The `TarballResolution` type declares `integrity` as optional (`integrity?: string`). When the lockfile omits the `integrity` field, the guard evaluates to `false`, skipping hash verification entirely. The worker then computes a new hash from the unverified content and stores it as legitimate. ```typescript // worker/src/start.ts:189-204 function addTarballToStore ({ buffer, storeDir, integrity, ... }: TarballExtractMessage) { if (integrity) { // false when integrity is undefined const { algorithm, hexDigest } = parseIntegrity(integrity) const calculatedHash = crypto.hash(algorithm, buffer, 'hex') if (calculatedHash !== hexDigest) { return { status: 'error', error: { type: 'integrity_validation_failed', ... } } } } return { status: 'success', value: { integrity: integrity ?? calcIntegrity(buffer) }, } } ``` ## Proof of Concept ```bash bash autofyn_audit/exploits/vuln1_integrity_bypass/exploit.sh # Publishes a package, generates lockfile, republishes tampered version, # strips integrity field, re-runs install --frozen-lockfile. # Result: PASS -- tampered package installed without integrity error. ``` ## Impact Supply chain compromise in environments where an attacker can both alter the lockfile and cause the referenced registry URL to serve altered package content. The `--frozen-lockfile` flag does not fail closed when the integrity field is missing. ## Suggested Remediation Require an `integrity` field for remote tarball resolutions. Change the `if (integrity)` guard to fail when integrity is absent for non-local packages. When `--frozen-lockfile` is active, reject lockfile entries that lack integrity for remote packages. --- > Discovered by [AutoFyn](https://github.com/SignalPilot-Labs/AutoFyn) > Full audit report: [audit_report.md](https://github.com/tempcollab/pnpm/blob/main/autofyn_audit/audit_report.md) > Exploit script: [exploit.sh](https://github.com/tempcollab/pnpm/blob/main/autofyn_audit/exploits/vuln1_integrity_bypass/exploit.sh)