An exploitable shared memory permissions vulnerability exists in the functionality of X11 Mesa 3D Graphics Library 19.1.2. An attacker can access the shared memory without any specific permissions to trigger this vulnerability.
https://usn.ubuntu.com/4271-1/
https://talosintelligence.com/vulnerability_reports/TALOS-2019-0857
https://lists.freedesktop.org/pipermail/mesa-dev/2019-October/223704.html
https://lists.debian.org/debian-lts-announce/2019/11/msg00013.html
https://gitlab.freedesktop.org/mesa/mesa/-/commit/02c3dad0f3b4d26e0faa5cc51d06bc50d693dcdc
http://lists.opensuse.org/opensuse-security-announce/2020-01/msg00037.html