From fc01bcb6f121ec06ba8ac761d9909f2fef9f30aa Mon Sep 17 00:00:00 2001
From: James Garbutt <43081j@users.noreply.github.com>
Date: Thu, 3 Sep 2026 10:13:28 +0100
Subject: [PATCH] fix: escape all cmd/bat file args

---
 src/normalize.ts            | 13 +++++++------
 src/test/main_test.ts       | 11 +++++++++++
 src/test/normalize_test.ts  | 17 +++++++++++++++++
 test/fixtures/echo_args.cmd |  2 ++
 4 files changed, 37 insertions(+), 6 deletions(-)
 create mode 100644 test/fixtures/echo_args.cmd

diff --git a/src/normalize.ts b/src/normalize.ts
index ab9a618..3ab6221 100644
--- a/src/normalize.ts
+++ b/src/normalize.ts
@@ -13,7 +13,7 @@ import {getPathFromEnv} from './env.js';
 const metaCharsRegExp = /([()\][%!^"`<>&|;, *?])/g;
 const shebangRegExp = /^#!\s*(.+)/;
 const isWindowsExecutableRegExp = /\.(?:com|exe)$/i;
-const isNodeModulesCmdRegExp = /node_modules[\\/]\.bin[\\/][^\\/]+\.cmd$/i;
+const isBatchFileRegExp = /\.(?:cmd|bat)$/i;
 const isWindows = process.platform === 'win32';
 const defaultPathExt = ['.EXE', '.CMD', '.BAT', '.COM'];
 const noPathExt = [''];
@@ -84,12 +84,13 @@ export function normalizeSpawnCommand(
 
   // We don't need a shell if the command filename is resolved and an executable
   if (file === null || !isWindowsExecutableRegExp.test(file)) {
-    // Need to double escape meta chars if the command is a cmd-shim located in `node_modules/.bin/`
-    // The cmd-shim simply calls execute the package bin file with NodeJS, proxying any argument
-    // Because the escape of metachars with ^ gets interpreted when the cmd.exe is first called,
-    // we need to double escape them
+    // Meta chars need double escaping if the command is a batch file. cmd.exe
+    // basically consumes the first layer of escaping.
+    // 1. `cmd.exe /c "command.cmd arg1 arg2"`
+    // 2. `command.cmd` sees `arg1` and `arg2` as `%1` and `%2`
+    // 3. `command.cmd` subs those in as actual commands
     const needsDoubleEscapeMetaChars =
-      file !== null && isNodeModulesCmdRegExp.test(file);
+      file !== null && isBatchFileRegExp.test(file);
 
     // Normalize posix paths into OS compatible paths (e.g.: foo/bar -> foo\bar)
     // This is necessary otherwise it will always fail with ENOENT in those cases
diff --git a/src/test/main_test.ts b/src/test/main_test.ts
index dbb5cba..ecc757c 100644
--- a/src/test/main_test.ts
+++ b/src/test/main_test.ts
@@ -225,6 +225,17 @@ if (isWindows) {
       );
       expect(result.stdout).toBe('');
     });
+
+    test('double escapes for batch files', async () => {
+      const result = await x(path.join(fixturesDir, 'echo_args.cmd'), [
+        '"&echo INJECTED'
+      ]);
+
+      // the batch file echoes `%*`, so the arg text itself is expected in
+      // stdout. a line of its own means `&` was parsed as a separator
+      expect(result.stdout).toContain('&echo INJECTED');
+      expect(result.stdout.split(/\r?\n/)).not.toContain('INJECTED');
+    });
   });
 
   describe('exec (windows) (async)', () => {
diff --git a/src/test/normalize_test.ts b/src/test/normalize_test.ts
index fdd12ca..d66513f 100644
--- a/src/test/normalize_test.ts
+++ b/src/test/normalize_test.ts
@@ -79,6 +79,23 @@ describe('normalizeSpawnCommand', () => {
       expect(normalized.args).toEqual([scriptPath]);
     });
 
+    test('double escapes meta chars in args to a batch file', () => {
+      const cmdPath = path.join(fixturesPath, 'echo_args.cmd');
+      const normalized = normalizeSpawnCommand(cmdPath, ['"&injected']);
+
+      // the batch interpreter consumes a second layer of `^` escapes when it
+      // expands `%*`, so `&` must still be escaped at that point
+      expect(normalized.args[3]).toBe(
+        `"${cmdPath} ^^^"\\^^^"^^^&injected^^^""`
+      );
+    });
+
+    test('single escapes meta chars in args to a non-batch command', () => {
+      const normalized = normalizeSpawnCommand('nonexistent', ['"&injected']);
+
+      expect(normalized.args[3]).toBe('"nonexistent ^"\\^"^&injected^""');
+    });
+
     test('handles relative commands without extension', () => {
       const relativePath = path.relative(
         cwd,
diff --git a/test/fixtures/echo_args.cmd b/test/fixtures/echo_args.cmd
new file mode 100644
index 0000000..4a4a371
--- /dev/null
+++ b/test/fixtures/echo_args.cmd
@@ -0,0 +1,2 @@
+@echo off
+echo %*