/usr/share/netgen/libsrc/csg/ is in netgen-headers 4.9.13.dfsg-8build2.
This file is owned by root:root, with mode 0o755.
..
/usr/share/netgen/libsrc/csg/algprim.hpp
/usr/share/netgen/libsrc/csg/brick.hpp
/usr/share/netgen/libsrc/csg/csg.hpp
/usr/share/netgen/libsrc/csg/csgeom.hpp
/usr/share/netgen/libsrc/csg/csgparser.hpp
/usr/share/netgen/libsrc/csg/curve2d.hpp
/usr/share/netgen/libsrc/csg/edgeflw.hpp
/usr/share/netgen/libsrc/csg/explicitcurve2d.hpp
/usr/share/netgen/libsrc/csg/extrusion.hpp
/usr/share/netgen/libsrc/csg/gencyl.hpp
/usr/share/netgen/libsrc/csg/geoml.hpp
/usr/share/netgen/libsrc/csg/identify.hpp
/usr/share/netgen/libsrc/csg/manifold.hpp
/usr/share/netgen/libsrc/csg/meshsurf.hpp
/usr/share/netgen/libsrc/csg/polyhedra.hpp
/usr/share/netgen/libsrc/csg/revolution.hpp
/usr/share/netgen/libsrc/csg/singularref.hpp
/usr/share/netgen/libsrc/csg/solid.hpp
/usr/share/netgen/libsrc/csg/specpoin.hpp
/usr/share/netgen/libsrc/csg/spline3d.hpp
/usr/share/netgen/libsrc/csg/surface.hpp
/usr/share/netgen/libsrc/csg/triapprox.hpp