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Published: 26 May 2021

A privilege escalation flaw was found in the Xorg-x11-server due to a lack of authentication for X11 clients. This flaw allows an attacker to take control of an X application by impersonating the server it is expecting to connect to.


as of 2021-05-19, there is no upstream fix for this issue. This
is a long-standing X11 design limitation and is difficult to
exploit. We will not be releasing updates for this issue.



Cvss 3 Severity Score


Score breakdown


Package Release Status
Launchpad, Ubuntu, Debian
impish Ignored

jammy Ignored

bionic Ignored

focal Ignored

groovy Ignored

hirsute Ignored

trusty Ignored

upstream Needed

xenial Ignored

Severity score breakdown

Parameter Value
Base score 7.0
Attack vector Local
Attack complexity High
Privileges required Low
User interaction None
Scope Unchanged
Confidentiality High
Integrity impact High
Availability impact High
Vector CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H