Can you describe your leak? And what was the overall conditions when it happened. I am assuming you where out camping. The reason I ask is the tent ends are known to have a condensation build up on the canvas especially at night. Leaky seams that is a different issue all together.
If it is condensation, that you are mistaken for a water leak, here is how I solved the problem. I open one of the tent end side windows just a few inches every night. I keep the opened portion in the high corner and just pull the canvas window cover away from the screen to encourage a little air flow. By doing it in an upper corner if it is raining it is protected from the rain and run off. Then I open my bathroom vent window a minimum of a ½ inch. Once we started this technique we have eliminated all of our condensation.
If it is a stitched seam that is leaking, I wish I had a good solution. I just posted this on another persons post that was having leaky seam issues. I am not sure it is a viable solution, but I think it would be worth a try.
Jaycoforum - leaking bunk end seams