Front catalytic converters are prone to cracking along the seams of the converter itself. Most repair shops can successfully weld the seems to prevent exhaust leakage.
Car Problem Reports
Infiniti QX4 Front Catalytic Converters are Prone to Cracking
Infiniti QX4 Problem
Visitor, 2002 Infiniti QX4
Check engine light came on right after picking up car from dealer for recall repairs. Looked up diagnostic code which said it needs catalytic system repairs