RSA Signature Forgery — Mozilla

Philip Mackenzie and Marius Schilder of Google informed us of Daniel Bleichenbacher’s recent presentation of a common implementation error in RSA signature verification, a failure to account for extra data in the signature. For signatures with a small exponent such as 3 it is possible for an attacker to calculate a value for this extra data to make an altered message appear to be correctly signed, allowing the signature to be forged. Mozilla’s Network Security Services (NSS) library was vulnerable to this flaw.