Shescape is a simple shell escape package for JavaScript. Versions prior to 1.5.8 were found to be subject to code injection on windows. This impacts users that use Shescape (any API function) to escape arguments for cmd.exe on Windows An attacker can omit all arguments following their input by including a line feed character (`'\n'`) in the payload. This bug has been patched in [v1.5.8] which you can upgrade to now. No further changes are required. Alternatively, line feed characters (`'\n'`) can be stripped out manually or the user input can be made the last argument (this only limits the impact).

Affected: npm: shescape

### Impact

This impacts users that use Shescape (any API function) to escape arguments for **cmd.exe** on **Windows**. An attacker can omit all arguments following their input by including a line feed character (`'\n'`) in the payload. Example:

```javascript import cp from "node:child_process"; import * as shescape from "shescape";

// 1. Prerequisites const options = { shell: "cmd.exe", };

// 2. Attack const payload = "attacker\n";

// 3. Usage let escapedPayload; escapedPayload = shescape.escape(payload, options); // Or escapedPayload = shescape.escapeAll([payload], options)[0]; // Or escapedPayload = shescape.quote(payload, options); // Or escapedPayload = shescape.quoteAll([payload], options)[0];

cp.execSync(`echo Hello ${escapedPayload}! How are you doing?`, options); // Outputs: "Hello attacker" ```

> **Note**: `execSync` is just illustrative here, all of `exec`, `execFile`, `execFileSync`, `fork`, `spawn`, and `spawnSync` can be attacked using a line feed character if CMD is the shell being used.

### Patches

This bug has been patched in [v1.5.8] which you can upgrade to now. No further changes are required.

### Workarounds

Alternatively, line feed characters (`'\n'`) can be stripped out manually or the user input can be made the last argument (this only limits the impact).

### References

- https://github.com/ericcornelissen/shescape/pull/332 - https://github.com/ericcornelissen/shescape/releases/tag/v1.5.8

### For more information

If you have any quest…