There is no cap on attributes, other than the technical limit of storing the values in 4 bytes in one of the save files. Actually, you can not max (FF FF FF FF = 4,294,967,295) the stat values; you can get up around 90 million, but closer to a billion there start to be issues (with strength, for example, the weight capacity becomes negative, and at higher values the strength itself becomes negative).


Practically, though, you are limited by level, equipment bonuses, the number of charm slots (up to 5 per piece of equipment, with up to 10 stat points per slot, using gold charms), etc.
At the end of my first game my stats were as follows (the number in brackets indicates the values with no equipment, without Finnigan's lockpicks in my inventory). I had plenty of gold charms I could have used, if needed.

Code
Level 53 Warrior

Vitality     1260    (444)
Magic         574     (30)

Strength      145    (111)
Agility       150    (112)
Intelligence   18     (10)
Constitution  100     (74)
Offense       124     (89)
Defense       108     (78)

Damage      139-178  (54-64)
Armour        484      (0)

Lightning Resistance   95 (25)
Fire Resistance       110 (25)
Poison Resistance      35 (25)
Spirit Resistance      95 (25)

Reputation     51
Weight       4500    (3820)