In this paper, we explore a new type of key collisions called target-plaintext key collisions of AES, which emerge as an open problem in the key committing security and are directly converted into single-block collision attacks on Davies-Meyer (DM) hashing mode. For this key collision, a ciphertext collision is uniquely observed when a specific plaintext is encrypted under two distinct keys. We introduce an efficient automatic search tool that leverages bit-wise behaviors of differential characteristics and dependencies among operations and internal variables. As a result, we demonstrate single-block collision attacks on 2/5/6-round AES-128/192/256-DM and semi-free-start collision attacks on 5/7/9-round AES-128/192/256-DM, respectively. Furthermore, by exploiting a specific class of free-start collisions with our tool, we present two-block collision attacks on 3/9-round AES-128/256-DM, respectively.