The vrend_decode_reset function in vrend_decode.c in virglrenderer before 0.6.0 allows local guest OS users to cause a denial of service (NULL pointer dereference and QEMU process crash) by destroying context 0 (zero).
https://security.gentoo.org/glsa/201707-06
https://lists.freedesktop.org/archives/virglrenderer-devel/2017-February/000145.html
https://cgit.freedesktop.org/virglrenderer/commit/?id=0a5dff15912207b83018485f83e067474e818bab
https://bugzilla.redhat.com/show_bug.cgi?id=1426170