GHSA-xpqm-wm3m-f34h

### Summary A path traversal vulnerability in pnpm's bin linking allows malicious npm packages to create executable shims or symlinks outside of `node_modules/.bin`. Bin names starting with `@` bypass validation, and after scope normalization, path traversal sequences like `../../` remain intact.

### Details The vulnerability exists in the bin name validation and normalization logic:

**1. Validation Bypass (`pkg-manager/package-bins/src/index.ts`)**

The filter allows any bin name starting with `@` to pass through without validation:

```typescript .filter((commandName) => encodeURIComponent(commandName) === commandName || commandName === '' || commandName[0] === '@' // <-- Bypasses validation ) ```

**2. Incomplete Normalization (`pkg-manager/package-bins/src/index.ts`)**

```typescript function normalizeBinName (name: string): string { return name[0] === '@' ? name.slice(name.indexOf('/') + 1) : name } // Input: @scope/../../evil // Output: ../../evil <-- Path traversal preserved! ```

**3. Exploitation (`pkg-manager/link-bins/src/index.ts:288`)**

The normalized name is used directly in `path.join()` without validation.

### PoC 1. Create a malicious package: ```json { "name": "malicious-pkg", "version": "1.0.0", "bin": { "@scope/../../.npmrc": "./malicious.js" } } ```

2. Install the package: ```bash pnpm add /path/to/malicious-pkg ```

3. Observe `.npmrc` created in project root (outside node_modules/.bin).

### Impact - All pnpm users who install npm packages - CI/CD pipelines using pnpm - Can overwrite config files, scripts, or other sensitive files

Verified on pnpm main @ commit 5a0ed1d45.