libical 1.0 allows remote attackers to cause a denial of service (use-after-free) via a crafted ics file.
https://usn.ubuntu.com/3897-1/
https://security.gentoo.org/glsa/201904-07
https://security.gentoo.org/glsa/201904-02
https://github.com/libical/libical/issues/286
https://github.com/libical/libical/issues/251
https://github.com/libical/libical/issues/235
https://bugzilla.mozilla.org/show_bug.cgi?id=1275400
https://access.redhat.com/errata/RHSA-2019:0270
https://access.redhat.com/errata/RHSA-2019:0269
http://www.securityfocus.com/bid/91459