Shescape is a simple shell escape library for JavaScript. Prior to 2.1.14 and 3.0.1, getEscapeFunction in src/internal/win/cmd.js does not escape `(` and `)` when applications use the escape or escapeAll APIs on Windows with shell set to cmd.exe, or with shell set to true when CMD is the default. An attacker-controlled argument can break out of a parenthesized CMD construct and inject shell syntax depending on the original command, resulting in arbitrary command execution. This issue is fixed in versions 2.1.14 and 3.0.1.

Affected: npm: shescape

### Impact

This impacts users of Shescape on Windows that explicitly configure `shell` to CMD, or `true` with the default shell being CMD, using the `escape` and `escapeAll` APIs.

An attacker may be able to achieve shell injection depending on the original command.

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

// 1. Prerequisites const options = { shell: "cmd.exe", // Or shell: true, // Only if the default shell is CMD };

// 2. Payload const payload = "x) else if a==a (echo y";

// 3. Usage const shescape = new Shescape(options); let escapedPayload;

escapedPayload = shescape.escape(payload); // Or escapedPayload = shescape.escapeAll([payload]);

// And (example) const result = cp.execSync(`if defined FALSY (echo ${escapedPayload})`, options);

// 4. Impact console.log(result.toString()); // Outputs "y" instead of ""

```

### Patches

This bug has been patched in [v2.1.14] and [v3.0.1] which you can upgrade to now.

If you are already using v3 of Shescape, no further changes are required. If you are using v2 of Shescape is recommended to upgrade as this version reaches end-of-life status on 2026-09-28, follow the [migration guide] to upgrade to v3.

No patches will be released for version of Shescape lower than v2.0.0.

### Workarounds

Alternatively, users of Shescape can remove all instances of `(` and `)` from untrusted inputs.

### For more information

- Comment on Pull Request [#2651] for v2 and [#2649] f…