Versions mentioned in the description apply to the upstream
Remediation section below for
Debian:9 relevant versions.
A flaw was found in xorg-x11-server in versions before 1.20.11. An integer underflow can occur in xserver which can lead to a local privilege escalation. The highest threat from this vulnerability is to data confidentiality and integrity as well as system availability.
xorg-server to version 2:1.19.2-1+deb9u8 or higher.