pax_decode_header in sparse.c in GNU Tar before 1.32 had a NULL pointer dereference when parsing certain archives that have malformed extended headers.
https://www.cisa.gov/news-events/ics-advisories/icsa-24-284-16
https://bugs.launchpad.net/ubuntu/+source/tar/+bug/1810241
http://savannah.gnu.org/bugs/?55369
http://lists.opensuse.org/opensuse-security-announce/2019-04/msg00077.html
http://git.savannah.gnu.org/cgit/tar.git/commit/?id=cb07844454d8cc9fb21f53ace75975f91185a120