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Ubuntu Security Notice USN-4614-1
November 03, 2020
gdm3 vulnerability
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A security issue affects these releases of Ubuntu and its derivatives:
– Ubuntu 20.10
– Ubuntu 20.04 LTS
– Ubuntu 18.04 LTS
Summary:
GDM could be made to create privileged users.
Software Description:
– gdm3: GNOME Display Manager
Details:
Kevin Backhouse discovered that GDM incorrectly launched the initial setup
tool when the accountsservice daemon was not reachable. A local attacker
able to cause accountsservice to crash or stop responding could trick GDM
into launching the initial setup tool and create a privileged user.
Update instructions:
The problem can be corrected by updating your system to the following
package versions:
Ubuntu 20.10:
gdm3 3.38.1-2ubuntu1.1
Ubuntu 20.04 LTS:
gdm3 3.36.3-0ubuntu0.20.04.2
Ubuntu 18.04 LTS:
gdm3 3.28.3-0ubuntu18.04.6
After a standard system update you need to reboot your computer to make
all the necessary changes.
References:
https://usn.ubuntu.com/4614-1
CVE-2020-16125
Package Information:
https://launchpad.net/ubuntu/+source/gdm3/3.38.1-2ubuntu1.1
https://launchpad.net/ubuntu/+source/gdm3/3.36.3-0ubuntu0.20.04.2
https://launchpad.net/ubuntu/+source/gdm3/3.28.3-0ubuntu18.04.6
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