Q: How should I state in my academic CV the impact factor of the journals I've published in?

That's an interesting question! Ideally, you would mention the impact factor of the years in which your paper was published, not the revised one. You could also mention with each published work whether the journal you have published in is indexed by a database; this could be presented as additional information within parentheses Remember that the impact factor is not constant. It will keep changing every two years. So updating the impact factor of every journal mentioned in your CV is impractical. There is a possibility that at the time of CV screening, the journal score may not match the current one. But you could explain that to the evaluators during your application/discussions.

Also, there are mixed views about the practice of using the impact factor on a CV. Some believe that this is field specific, i.e., in certain field you don't really need to mention the impact factor of a journal on your CV because everybody knows the top journals in that field, irrespective of their impact factors. But some feel that this practice should be avoided because it indicates an excessive reliance on the impact factor, which has recently begun losing its importance as the most important parameter to judge the quality of a journal or researcher. There is also the possibility that the person who reviews your CV does not believe in using the impact factor, but instead relies on the value of what you have done to gauge your potential. More and more researchers and funders are looking at other indicators such as altmetrics or a combination of metrics.

So try finding out what is most commonly followed in your field, and check whether the funding body/institution you are applying to focuses on the impact factor to evaluate applications. And consider adding additional metrics to your CV to show other ways in which your research has had an impact.