CVE-2026-50021 — pnpm
MEDIUMCVE-2026-50021 is a medium-severity (CVSS 6.8) CWE-354 vulnerability in pnpm. A fix is available for pnpm — see the affected versions and patch details below.
pnpm: Integrity Check Bypass via Missing Lockfile Integrity Field
Exploitation Status
Proof-of-concept exploit code exists
- CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.
- A successful exploit gives an attacker total control of the affected component, not partial access.
Exploitation and automatability from CISA’s SSVC triage for CVE-2026-50021.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
CVE-2026-50021 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.
Where this sits among everything scored
Of 380,066 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.
Real-World Exposure
How broadly this vulnerability is actually deployed: weekly install volume shows current usage, and reverse-dependency count shows how many other packages break if it stays unpatched.
pnpmnpmDescription
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.
// 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 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 Full audit report: audit_report.md Exploit script: exploit.sh
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | pnpm | ≥ 11.0.0&&< 11.4.0 | 11.4.0npm install pnpm@11.4.0 |
| 📦npm | pnpm | all versions | 10.34.1npm install pnpm@10.34.1 |
Affected Products
pnpmpnpmDetection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for pnpm, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update pnpm to 11.4.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-50021 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
Frequently Asked Questions
Is CVE-2026-50021 in your dependencies?
Find it across npm, including transitive dependencies.