/usr/share/doc/libsundials-serial-dev/examples/cvodes/serial/ is in libsundials-serial-dev 2.5.0-3+b3.
This file is owned by root:root, with mode 0o755.
..
/usr/share/doc/libsundials-serial-dev/examples/cvodes/serial/README
/usr/share/doc/libsundials-serial-dev/examples/cvodes/serial/cvsAdvDiff_ASAi_bnd.c
/usr/share/doc/libsundials-serial-dev/examples/cvodes/serial/cvsAdvDiff_FSA_non.c
/usr/share/doc/libsundials-serial-dev/examples/cvodes/serial/cvsAdvDiff_bnd.c
/usr/share/doc/libsundials-serial-dev/examples/cvodes/serial/cvsAdvDiff_bndL.c
/usr/share/doc/libsundials-serial-dev/examples/cvodes/serial/cvsDirectDemo_ls.c
/usr/share/doc/libsundials-serial-dev/examples/cvodes/serial/cvsDiurnal_FSA_kry.c
/usr/share/doc/libsundials-serial-dev/examples/cvodes/serial/cvsDiurnal_kry.c
/usr/share/doc/libsundials-serial-dev/examples/cvodes/serial/cvsDiurnal_kry_bp.c
/usr/share/doc/libsundials-serial-dev/examples/cvodes/serial/cvsFoodWeb_ASAi_kry.c
/usr/share/doc/libsundials-serial-dev/examples/cvodes/serial/cvsFoodWeb_ASAp_kry.c
/usr/share/doc/libsundials-serial-dev/examples/cvodes/serial/cvsHessian_ASA_FSA.c
/usr/share/doc/libsundials-serial-dev/examples/cvodes/serial/cvsKrylovDemo_ls.c
/usr/share/doc/libsundials-serial-dev/examples/cvodes/serial/cvsKrylovDemo_prec.c
/usr/share/doc/libsundials-serial-dev/examples/cvodes/serial/cvsRoberts_ASAi_dns.c
/usr/share/doc/libsundials-serial-dev/examples/cvodes/serial/cvsRoberts_FSA_dns.c
/usr/share/doc/libsundials-serial-dev/examples/cvodes/serial/cvsRoberts_dns.c
/usr/share/doc/libsundials-serial-dev/examples/cvodes/serial/cvsRoberts_dnsL.c
/usr/share/doc/libsundials-serial-dev/examples/cvodes/serial/cvsRoberts_dns_uw.c