If an egg cracks during sous vide cooking, the egg white will leak out into the water bath, resulting in a messy and potentially unappetizing outcome. The egg may still be edible, but the texture will be compromised.
When an egg cracks during sous vide, the pressure difference between the inside of the egg and the water bath forces the liquid egg white to escape through the crack. This can create wispy strands of cooked egg white floating in the water. While the yolk might remain intact and cook properly, the loss of egg white will affect the overall texture and presentation. The water bath itself won't penetrate the shell significantly unless the crack is very large, but the leaking egg white is the primary concern. The egg is still safe to eat as long as the water bath temperature was high enough to pasteurize the egg, but the aesthetic appeal and texture will be diminished.
To prevent eggs from cracking during sous vide, preheat the eggs in warm tap water for a few minutes before placing them in the sous vide bath. This reduces the thermal shock and minimizes the risk of cracking.