Code: file_transfer_t *imcb_file_send_start(struct im_connection *ic, char *handle, char *file_name, size_t file_size)
{
 	bee_t *bee = ic->bee;
 	bee_user_t *bu = bee_user_by_handle(bee, ic, handle);
 
	if (bee->ui->ft_in_start) {
 		return bee->ui->ft_in_start(bee, bu, file_name, file_size);
 	} else {
 		return NULL;
	}
}

Vulnerability Type: DoS Exec Code 
CWE ID: CWE-476
Summary: BitlBee before 3.5 allows remote attackers to cause a denial of service (NULL pointer dereference and crash) and possibly execute arbitrary code via a file transfer request for a contact that is not in the contact list.
Commit Message: imcb_file_send_start: handle ft attempts from non-existing users