This is the primary official source. Patched versions are typically found under the "Solutions" tab (Patch Releases), while the base installer is under the "Products" tab (ISO Releases).
Never run the base 6.7 U3 ISO in production – you will be rolling out a hypervisor with three-year-old bugs. Use the patched version, verify the SHA256, and enjoy a stable virtualization platform until you are ready to migrate to vSphere 8. vmware esxi 67 u3 download iso patched
It is critical to understand: Instead, they publish a new "Update" ISO only when a major Update (e.g., U3a, U3b) is needed. For ESXi 6.7, there was never an "U3c" or "U3d" ISO. This is the primary official source