Cherry-picked putty to fix CVE-2024-31497. If you have used a 521-bit ECDSA private key with any previous version of PuTTY, consider the private key compromised: remove the public key from authorized_keys files, and generate a new key pair.
However, this only affects that one algorithm and key size. No other size of ECDSA key is affected, and no other key type is affected.
