Though Kant's deontic ethics has been correctly cited, I am not sure that a "categorical" imperative is exactly the same as an "absolute" imperative. And I am not sure that "absolute moral value" makes sense internally.
First, it appears from my Kant dictionary (Blackwell) that Kant is ambivalent about "the absolute," and while discussing it in CPR never actually applies that term to the categorical imperative. The absolute is not, of course, the sort of thing that can be "known" and in that way enter into judgements.
Second, "value" by almost any definition is relative to some value system, ideal, or "general equivalent." (In Kant's terms "hypothetical imperative.") I think most philosophers agree that this is a very problematic area of Kant's philosophy. He seems to depend implicitly on tweaking assumptions of freedom, limits of knowledge, and divine law in ways that have little if any clear practical application.
If we must read his categorical imperative as a kind of guiding ideal or limit test, then is it correct to say that it generates "absolute values"? When he suggests as much for the "good will" or the "person" as an end, things get pretty vague and these ideals seem to stand outside of any real "value" system. Values are relational, and I am not sure that the ground or "axiom" of some value system is itself a "value."
Anyway, I am only suggesting that Kant or other deontic ethicists might not be entirely clear on precisely this point, and that combining the terms "value" and "absolute" may be problematic.I admit I am not deeply familiar with Kant. But I do not see how one can, in the end, successfully combine a structural limit on knowledge with an "absolute" standard for practical judgments, except by appeal to faith.