test: add test for spawn path traversal with access errors

Adds a test case that places inaccessible directories and files in PATH
to verify that spawn correctly returns ENOENT for non-existent commands,
ensuring robustness of the EACCES handling fix.

Author: watilde

lib/internal/child_process.js

@@ -87,9 +87,7 @@ function verifyENOENT(file, envPairs) {
       }
     }
   }
-  if (!envPath) {
-    envPath = process.env.PATH;
-  }
+  envPath ||= process.env.PATH;
   if (!envPath) return false;
   const paths = envPath.split(path.delimiter);
   for (let i = 0; i < paths.length; i++) {

test/parallel/test-child-process-spawn-path-access.js

@@ -0,0 +1,62 @@
+'use strict';
+const common = require('../common');
+const assert = require('assert');
+const cp = require('child_process');
+const fs = require('fs');
+const path = require('path');
+
+const tmpdir = require('../common/tmpdir');
+tmpdir.refresh();
+
+// Scenario: PATH contains directories that are inaccessible or are actually files.
+// The system spawn (execvp) might return EACCES in these cases on some platforms.
+// We want to ensure Node.js consistently reports ENOENT if the command is truly missing.
+
+const noPermDir = path.join(tmpdir.path, 'no-perm-dir');
+fs.mkdirSync(noPermDir);
+
+const fileInPath = path.join(tmpdir.path, 'file-in-path');
+fs.writeFileSync(fileInPath, '');
+
+if (!common.isWindows) {
+  try {
+    fs.chmodSync(noPermDir, '000');
+  } catch (e) {
+    // If we can't chmod (e.g. root or weird fs), skip the permission part of the test
+    // but keep the structure.
+    console.log('# Skipped chmod 000 on no-perm-dir due to error:', e.message);
+  }
+}
+
+// Ensure cleanup restores permissions so tmpdir can be removed
+process.prependListener('exit', () => {
+  if (!common.isWindows && fs.existsSync(noPermDir)) {
+    try {
+      fs.chmodSync(noPermDir, '777');
+    } catch {
+      // Ignore cleanup errors during exit
+    }
+  }
+});
+
+const env = { ...process.env };
+const sep = path.delimiter;
+
+// Prepend the problematic entries to PATH
+env.PATH = `${noPermDir}${sep}${fileInPath}${sep}${env.PATH}`;
+
+const command = 'command-that-does-not-exist-at-all-' + Date.now();
+
+const child = cp.spawn(command, { env });
+
+child.on('error', common.mustCall((err) => {
+  assert.strictEqual(err.code, 'ENOENT');
+  assert.strictEqual(err.syscall, `spawn ${command}`);
+}));
+
+// Also test sync
+try {
+  cp.spawnSync(command, { env });
+} catch (err) {
+  assert.strictEqual(err.code, 'ENOENT');
+}