Update with CFLoop

There is nothing in your update query to distinguish the individual records.

I have no idea what you are attempting to accomplish, but this is how I read your code and I find its purpose quite confusing.

Read a set of records where id = #attributes.id#

<cfquery name="q" datasource="x">
  select *
  from table1
  where id=#attributes.id#
  order by data_vencimento
</cfquery>

Iterate over each of the records in this set.

<cfloop query ="q">

Each record initilze a counter to zero.

<cfset idx = 0>

Loop from 1 to the number of records in the record set, reusing the previously initlized counter.

<cfloop  index="idx" from="1" to="#q.recordcount#">

Add one to this counter|loop Index, effectivily jumping the loop counter ahead by one???

<cfset idx = idx+1>

Update all the records in the record set to the latest value in the counter|loop index variable

<cfquery name="q2" datasource="x">
  UPDATE table1
  SET column=<cfqueryparam value="#idx#" cfsqltype="cf_sql_integer"> 
  where id=#attributes.id# 
</cfquery>