A xorg-server security update has been released for Debian GNU/Linux 11 to address a use-after-free flaw.

DSA 5380-1: xorg-server security update

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Debian Security Advisory DSA-5380-1 security@debian.org
  https://www.debian.org/security/ Salvatore Bonaccorso
March 29, 2023   https://www.debian.org/security/faq
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Package : xorg-server
CVE ID : CVE-2023-1393

Jan-Niklas Sohn discovered that a user-after-free flaw in the Composite
extension of the X.org X server may result in privilege escalation if
the X server is running under the root user.

For the stable distribution (bullseye), this problem has been fixed in
version 2:1.20.11-1+deb11u6.

We recommend that you upgrade your xorg-server packages.

For the detailed security status of xorg-server please refer to its
security tracker page at:
  https://security-tracker.debian.org/tracker/xorg-server

Further information about Debian Security Advisories, how to apply
these updates to your system and frequently asked questions can be
found at:   https://www.debian.org/security/