[USN-7299-4] X.Org X Server regression

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Ubuntu Security Notice USN-7299-4
March 17, 2025

xorg-server, xorg-server-hwe-16.04, xorg-server-hwe-18.04 regression
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A security issue affects these releases of Ubuntu and its derivatives:

- Ubuntu 18.04 LTS
- Ubuntu 16.04 LTS

Summary:

Several security issues were fixed in X.Org X Server.

Software Description:
- xorg-server: X.Org X11 server
- xorg-server-hwe-18.04: X.Org X11 server
- xorg-server-hwe-16.04: X.Org X11 server

Details:

USN-7299-2 fix vulnerabilities in X.Org X Server. This fix caused
a regression in Ubuntu 16.04 LTS and Ubuntu 18.04 LTS. This update
fix the regression and re-apply the fix for the CVE listed.

We apologize for the inconvenience.

Original advisory details:

Jan-Niklas Sohn discovered that the X.Org X Server incorrectly handled
certain memory operations. An attacker could use these issues to cause the
X Server to crash, leading to a denial of service, or possibly execute
arbitrary code.

Update instructions:

The problem can be corrected by updating your system to the following
package versions:

Ubuntu 18.04 LTS
xserver-xorg-core 2:1.19.6-1ubuntu4.15+esm12
Available with Ubuntu Pro
xserver-xorg-core-hwe-18.04 2:1.20.8-2ubuntu2.2~18.04.11+esm4
Available with Ubuntu Pro
xwayland 2:1.19.6-1ubuntu4.15+esm12
Available with Ubuntu Pro
xwayland-hwe-18.04 2:1.20.8-2ubuntu2.2~18.04.11+esm4
Available with Ubuntu Pro

Ubuntu 16.04 LTS
xserver-xorg-core 2:1.18.4-0ubuntu0.12+esm17
Available with Ubuntu Pro
xserver-xorg-core-hwe-16.04 2:1.19.6-1ubuntu4.1~16.04.6+esm9
Available with Ubuntu Pro
xwayland 2:1.18.4-0ubuntu0.12+esm17
Available with Ubuntu Pro
xwayland-hwe-16.04 2:1.19.6-1ubuntu4.1~16.04.6+esm9
Available with Ubuntu Pro

After a standard system update you need to reboot your computer to make all
the necessary changes.

References:
https://ubuntu.com/security/notices/USN-7299-4
https://ubuntu.com/security/notices/USN-7299-3
https://ubuntu.com/security/notices/USN-7299-2
https://ubuntu.com/security/notices/USN-7299-1
CVE-2025-26594, CVE-2025-26595, CVE-2025-26596, CVE-2025-26597,
CVE-2025-26598, CVE-2025-26599, CVE-2025-26600, CVE-2025-26601,
https://launchpad.net/bugs/2102209