Summary
pnpm Has an Integrity Check Bypass via Missing Lockfile Integrity Field
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.
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
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.
CVE-2026-50021 has a CVSS score of 6.8 (Medium). The vector is network-reachable, low privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (11.4.0, 10.34.1); upgrading removes the vulnerable code path.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
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pnpm to 11.4.0 or later; pnpm to 10.34.1 or later
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Frequently Asked Questions
- What is CVE-2026-50021? CVE-2026-50021 is a medium-severity security vulnerability in pnpm (npm), affecting versions >= 11.0.0, < 11.4.0. It is fixed in 11.4.0, 10.34.1.
- How severe is CVE-2026-50021? CVE-2026-50021 has a CVSS score of 6.8 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
- Which versions of pnpm are affected by CVE-2026-50021? pnpm (npm) versions >= 11.0.0, < 11.4.0 is affected.
- Is there a fix for CVE-2026-50021? Yes. CVE-2026-50021 is fixed in 11.4.0, 10.34.1. Upgrade to this version or later.
- Is CVE-2026-50021 exploitable, and should I be worried? Whether CVE-2026-50021 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2026-50021 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2026-50021?
- Upgrade
pnpmto 11.4.0 or later - Upgrade
pnpmto 10.34.1 or later
- Upgrade