pnpm has Windows-specific tarball Path Traversal

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

6.5 · CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:N

EPSS

• CVE-2026-23889: 0.48% estimated exploitation activity in the next 30 days; percentile 41.70 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary A 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. This vulnerability is Windows-only. Details 1. Incomplete Path Normalization (store/cafs/src/parseTarball.ts:107-110) A path like foo\..\..\.npmrc does NOT contain ./ and bypasses this check. 2. Platform-Dependent Behavior (fs/indexed-pkg-importer/src/importIndexedDir.ts:97-98) - On Unix: Backslashes are literal filename characters (safe) - On Windows: Backslashes are directory separators (exploitable) PoC 1. Create a malicious tarball with entry package/foo\..\..\.npmrc 2. Host it or use as a tarball URL dependency 3. On Windows: pnpm install 4. Observe .npmrc written outside package directory Impact - Windows pnpm users - Windows CI/CD pipelines (GitHub Actions Windows runners, Azure DevOps) - Can overwrite…

Published by the source

26 Jan 2026, 21:02 UTC

Last modified by the source

3 Feb 2026, 03:06 UTC

Source last checked

26 Oct 2026, 12:41 UTC

1. Revision 2 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-6x96-7vc8-cm3p

2. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-6x96-7vc8-cm3p

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# Patch Next advisory brief: CVE-2026-23889

Advisory: pnpm has Windows-specific tarball Path Traversal
IDs: CVE-2026-23889, GHSA-6x96-7vc8-cm3p
Record: https://patchnext.com/advisories/cve-2026-23889 (revision 2, source checked 26 Oct 2026, 12:41 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 6.5)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: pnpm 10.28.1. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm pnpm: affected < 10.28.1; fixed in 10.28.1

## Suggested inspection (read-only)
- `npm ls pnpm --all`: lists every installed copy and version, including transitive ones. Run in the project root after `npm ci`.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on pnpm.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-6x96-7vc8-cm3p (OSV record GHSA-6x96-7vc8-cm3p lists affected ranges: npm pnpm >=0 <10.28.1 (fixed))
- Verified: https://github.com/advisories/GHSA-6x96-7vc8-cm3p (GitHub-reviewed advisory GHSA-6x96-7vc8-cm3p lists affected ranges: npm pnpm >=0 <10.28.1)

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