A sddm security update has been released for Debian GNU/Linux 10 to address an issue where a local attacker can take advantage of a race condition when creating the Xauthority file to escalate privileges.

DSA 4783-1: sddm security update

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Debian Security Advisory DSA-4783-1 security@debian.org
  https://www.debian.org/security/ Salvatore Bonaccorso
November 05, 2020   https://www.debian.org/security/faq
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Package : sddm
CVE ID : CVE-2020-28049
Debian Bug : 973748

Fabian Vogt discovered a flaw in sddm, a modern display manager for X11.
A local attacker can take advantage of a race condition when creating
the Xauthority file to escalate privileges.

For the stable distribution (buster), this problem has been fixed in
version 0.18.0-1+deb10u1.

We recommend that you upgrade your sddm packages.

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

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/