ProcEstablishConnection(ClientPtr client)
{
    const char *reason;
    char *auth_proto, *auth_string;
    xConnClientPrefix *prefix;

    REQUEST(xReq);

     prefix = (xConnClientPrefix *) ((char *) stuff + sz_xReq);
     auth_proto = (char *) prefix + sz_xConnClientPrefix;
     auth_string = auth_proto + pad_to_int32(prefix->nbytesAuthProto);
    if ((prefix->majorVersion != X_PROTOCOL) ||
         (prefix->minorVersion != X_PROTOCOL_REVISION))
         reason = "Protocol version mismatch";
     else

    return (SendConnSetup(client, reason));
}

The product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly.