psqlODBC copies the reply to a large-object read (loread) into the application's buffer using the length sent by the server, without comparing it to the buffer size. A server not trusted under current SSL settings, or a man-in-the-middle, can return more bytes than the buffer holds and overwrite adjacent memory in the client process with server-chosen bytes. Fetching any large-object column is sufficient to trigger it. Versions before psqlODBC 18.00.0006 are affected.