In PuTTY 0.68 through 0.80 before 0.81, biased ECDSA nonce generation allows an attacker…
In PuTTY 0.68 through 0.80 before 0.81, biased ECDSA nonce generation allows an attacker to recover a user's NIST P-521 secret key via a quick attack in approximately 60 signatures.