Affected versions of cookie-signature are vulnerable to timing attacks as a result of using a fail-early comparison instead of a constant-time comparison.

Timing attacks remove the exponential increase in entropy gained from increased secret length, by providing per-character feedback on the correctness of a guess via miniscule timing differences.

Under favorable network conditions, an attacker can exploit this to guess the secret in no more than charset*length guesses, instead of charset^length guesses required were the timing attack not present.

Update to 1.0.6 or later.