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.

wxBitcoin and bitcoind before 0.3.5 do not properly handle script opcodes in Bitcoin transactions, which allows remote attackers to spend bitcoins owned by other users via unspecified vectors.

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.

wxBitcoin and bitcoind 0.3.x allow remote attackers to cause a denial of service (electricity consumption) via a Bitcoin transaction containing multiple OP_CHECKSIG script opcodes.

wxBitcoin and bitcoind before 0.3.5 allow remote attackers to cause a denial of service (daemon crash) via a Bitcoin transaction containing an OP_LSHIFT script opcode.

wxBitcoin and bitcoind before 0.3.13 do not properly handle bitcoins associated with Bitcoin transactions that have zero confirmations, which allows remote attackers to cause a denial of service (invalid-transaction flood) by sending low-valued transactions without transaction fees.

Integer overflow in wxBitcoin and bitcoind before 0.3.11 allows remote attackers to bypass intended economic restrictions and create many bitcoins via a crafted Bitcoin transaction.