The alert functionality in bitcoind and Bitcoin-Qt before 0.7.0 supports different character representations of the same signature data, but relies on a hash of this signature, which allows remote attackers to cause a denial of service (resource consumption) via a valid modified signature for a circulating alert.

The Bitcoin protocol, as used in bitcoind before 0.4.4, wxBitcoin, Bitcoin-Qt, and other programs, does not properly handle multiple transactions with the same identifier, which allows remote attackers to cause a denial of service (unspendable transaction) by leveraging the ability to create a duplicate coinbase transaction.

The "encrypt wallet" feature in wxBitcoin and bitcoind 0.4.x before 0.4.1, and 0.5.0rc, does not properly interact with the deletion functionality of BSDDB, which allows context-dependent attackers to obtain unencrypted private keys from Bitcoin wallet files by bypassing the BSDDB interface and reading entries that are marked for deletion.