Security updates for Wednesday

Security updates have been issued by Debian (cgal, exim4, and mediawiki), Fedora (axel, libmicrohttpd, libtpms, perl-Image-ExifTool, pngcheck, python-yara, and yara), Gentoo (exim), Mageia (kernel-linus), openSUSE (bind and postsrsd), SUSE (avahi, openexr, p7zip, python-Pygments, python36, samba, sca-patterns-sle11, and webkit2gtk3), and Ubuntu (nvidia-graphics-drivers-390, nvidia-graphics-drivers-418-server, nvidia-graphics-drivers-450, nvidia-graphics-drivers-450-server, nvidia-graphics-drivers-460, nvidia-graphics-drivers-460-server).