/usr/include/CGAL/Circular_kernel_3/ is in libcgal-dev 4.2-5ubuntu1.
This file is owned by root:root, with mode 0o755.
..
/usr/include/CGAL/Circular_kernel_3/Circular_arc_3.h
/usr/include/CGAL/Circular_kernel_3/Circular_arc_point_3.h
/usr/include/CGAL/Circular_kernel_3/Line_arc_3.h
/usr/include/CGAL/Circular_kernel_3/function_objects_polynomial_sphere.h
/usr/include/CGAL/Circular_kernel_3/get_equation_object_on_curved_kernel_3.h
/usr/include/CGAL/Circular_kernel_3/interface_macros.h
/usr/include/CGAL/Circular_kernel_3/internal_function_compare_spherical_kernel.h
/usr/include/CGAL/Circular_kernel_3/internal_function_compare_to_right_spherical_kernel.h
/usr/include/CGAL/Circular_kernel_3/internal_function_has_on_spherical_kernel.h
/usr/include/CGAL/Circular_kernel_3/internal_functions_on_circle_3.h
/usr/include/CGAL/Circular_kernel_3/internal_functions_on_circular_arc_3.h
/usr/include/CGAL/Circular_kernel_3/internal_functions_on_circular_arc_point_3.h
/usr/include/CGAL/Circular_kernel_3/internal_functions_on_line_3.h
/usr/include/CGAL/Circular_kernel_3/internal_functions_on_line_arc_3.h
/usr/include/CGAL/Circular_kernel_3/internal_functions_on_plane_3.h
/usr/include/CGAL/Circular_kernel_3/internal_functions_on_sphere_3.h