Unchecked NULL pointer usage in LookupModMask in xkbcomp/expr.c in xkbcommon before 0.8.2 could be used by local attackers to crash (NULL pointer dereference) the xkbcommon parser by supplying a crafted keymap file with invalid virtual modifiers.
https://access.redhat.com/errata/RHSA-2019:2079
https://github.com/xkbcommon/libxkbcommon/commit/4e2ee9c3f6050d773f8bbe05bc0edb17f1ff8371
https://lists.freedesktop.org/archives/wayland-devel/2018-August/039243.html
https://security.gentoo.org/glsa/201810-05