A heap buffer overflow was found in virtio_crypto_sym_op_helper() in hw/virtio/virtio-crypto.c. It could occur while handling data encryption/dencryption requests in virtio_crypto_handle_sym_req(). There is no check for the value of the src_len and the dst_len in virtio_crypto_sym_op_helper(), so if src_len is not equal to dst_len, a heap based buff overflow occurs while encrypting/dencrypting the data.