path: fix win32 normalize false-positive on reserved names

lib/path.js

@@ -471,7 +471,7 @@ const win32 = {
       } while ((index = StringPrototypeIndexOf(path, ':', index + 1)) !== -1);
     }
     const colonIndex = StringPrototypeIndexOf(path, ':');
-    if (isWindowsReservedName(path, colonIndex)) {
+    if (colonIndex !== -1 && isWindowsReservedName(path, colonIndex)) {
       return `.\\${device ?? ''}${tail}`;
     }
     if (device === undefined) {

test/parallel/test-path-normalize.js

@@ -69,6 +69,17 @@ assert.strictEqual(path.win32.normalize('//server/share/dir/../../../?/D:/file')
 assert.strictEqual(path.win32.normalize('//server/goodshare/../badshare/file'),
                    '\\\\server\\goodshare\\badshare\\file');
 
+// A path is only a Windows reserved device name when the reserved name is
+// followed by a colon. A name that merely starts with a reserved name (and has
+// no colon) must be left untouched and not be prefixed with `.\`.
+assert.strictEqual(path.win32.normalize('CONx'), 'CONx');
+assert.strictEqual(path.win32.normalize('NULs'), 'NULs');
+assert.strictEqual(path.win32.normalize('LPT1x'), 'LPT1x');
+assert.strictEqual(path.win32.normalize('PRNzzz'), 'PRNzzz');
+assert.strictEqual(path.win32.normalize('CON'), 'CON');
+// With a trailing colon the reserved-name handling still applies.
+assert.strictEqual(path.win32.normalize('CON:'), '.\\CON:.');
+
 assert.strictEqual(path.posix.normalize('./fixtures///b/../b/c.js'),
                    'fixtures/b/c.js');
 assert.strictEqual(path.posix.normalize('/foo/../../../bar'), '/bar');