/usr/include/cupt/ is in libcupt3-dev 2.6.4.
This file is owned by root:root, with mode 0o755.
..
/usr/include/cupt/cache/
/usr/include/cupt/cache.hpp
/usr/include/cupt/cache/binarypackage.hpp
/usr/include/cupt/cache/binaryversion.hpp
/usr/include/cupt/cache/package.hpp
/usr/include/cupt/cache/relation.hpp
/usr/include/cupt/cache/releaseinfo.hpp
/usr/include/cupt/cache/sourcepackage.hpp
/usr/include/cupt/cache/sourceversion.hpp
/usr/include/cupt/cache/version.hpp
/usr/include/cupt/common.hpp
/usr/include/cupt/config.hpp
/usr/include/cupt/download/
/usr/include/cupt/download/manager.hpp
/usr/include/cupt/download/method.hpp
/usr/include/cupt/download/methodfactory.hpp
/usr/include/cupt/download/progress.hpp
/usr/include/cupt/download/progresses/
/usr/include/cupt/download/progresses/console.hpp
/usr/include/cupt/download/uri.hpp
/usr/include/cupt/file.hpp
/usr/include/cupt/format2.hpp
/usr/include/cupt/fwd.hpp
/usr/include/cupt/hashsums.hpp
/usr/include/cupt/range.hpp
/usr/include/cupt/system/
/usr/include/cupt/system/resolver.hpp
/usr/include/cupt/system/resolvers/
/usr/include/cupt/system/resolvers/native.hpp
/usr/include/cupt/system/snapshots.hpp
/usr/include/cupt/system/state.hpp
/usr/include/cupt/system/worker.hpp
/usr/include/cupt/versionstring.hpp