function checkValue(input, allowed) {
  const autoReject = (input.length !== allowed.length);
  if (autoReject) {
    // Prevent leaking length information by always making a comparison with the
    // same input when lengths don't match what we expect ...
    allowed = input;
  }
  const isMatch = timingSafeEqual(input, allowed);
  return (!autoReject && isMatch);
}
The software constructs all or part of an OS command using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the intended OS command when it is sent to a downstream component.