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:
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:
execSyncis just illustrative here, all ofexec,execFile,execFileSync,fork,spawn, andspawnSynccan be attacked using a line feed character if CMD is the shell being used.
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).
If you have any questions or comments about this advisory: