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[USN-8945-1] XZ Utils vulnerability

Posted on 20 October 2026
Ubuntu Security

==========================================================================Ubuntu Security Notice USN-8945-1
October 20, 2026

xz-utils vulnerability
==========================================================================
A security issue affects these releases of Ubuntu and its derivatives:

- Ubuntu 26.10
- Ubuntu 26.04 LTS
- Ubuntu 24.04 LTS
- Ubuntu 22.04 LTS
- Ubuntu 20.04 LTS
- Ubuntu 18.04 LTS
- Ubuntu 16.04 LTS
- Ubuntu 14.04 LTS

Summary:

XZ Utils could be made to crash or run programs if it processed
specially crafted compressed files under certain conditions.

Software Description:
- xz-utils: XZ-format compression utilities

Details:

It was discovered that XZ Utils incorrectly handled certain memory
allocation failures when reinitializing decoders for specific compressed
file formats. An attacker could possibly use this issue to trigger an
invalid memory write, resulting in a denial of service or arbitrary code
execution.

Update instructions:

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

Ubuntu 26.10
liblzma5 5.8.3-1ubuntu1
xz-utils 5.8.3-1ubuntu1
xzdec 5.8.3-1ubuntu1

Ubuntu 26.04 LTS
liblzma5 5.8.3-1ubuntu0.1
xz-utils 5.8.3-1ubuntu0.1
xzdec 5.8.3-1ubuntu0.1

Ubuntu 24.04 LTS
liblzma5 5.6.1+really5.4.5-1ubuntu0.4
xz-utils 5.6.1+really5.4.5-1ubuntu0.4
xzdec 5.6.1+really5.4.5-1ubuntu0.4

Ubuntu 22.04 LTS
liblzma5 5.2.5-2ubuntu1.2
xz-utils 5.2.5-2ubuntu1.2
xzdec 5.2.5-2ubuntu1.2

Ubuntu 20.04 LTS
liblzma5 5.2.4-1ubuntu1.1+esm2
Available with Ubuntu Pro
xz-utils 5.2.4-1ubuntu1.1+esm2
Available with Ubuntu Pro
xzdec 5.2.4-1ubuntu1.1+esm2
Available with Ubuntu Pro

Ubuntu 18.04 LTS
liblzma5 5.2.2-1.3ubuntu0.1+esm2
Available with Ubuntu Pro
xz-utils 5.2.2-1.3ubuntu0.1+esm2
Available with Ubuntu Pro
xzdec 5.2.2-1.3ubuntu0.1+esm2
Available with Ubuntu Pro

Ubuntu 16.04 LTS
liblzma5 5.1.1alpha+20120614-2ubuntu2.16.04.1+esm3
Available with Ubuntu Pro
xz-utils 5.1.1alpha+20120614-2ubuntu2.16.04.1+esm3
Available with Ubuntu Pro
xzdec 5.1.1alpha+20120614-2ubuntu2.16.04.1+esm3
Available with Ubuntu Pro

Ubuntu 14.04 LTS
liblzma5 5.1.1alpha+20120614-2ubuntu2.14.04.1+esm3
Available with Ubuntu Pro
xz-utils 5.1.1alpha+20120614-2ubuntu2.14.04.1+esm3
Available with Ubuntu Pro
xzdec 5.1.1alpha+20120614-2ubuntu2.14.04.1+esm3
Available with Ubuntu Pro

In general, a standard system update will make all the necessary changes.

References:
https://ubuntu.com/security/notices/USN-8945-1
https://bugs.launchpad.net/bugs/2170056

Package Information:
https://launchpad.net/ubuntu/+source/xz-utils/5.8.3-1ubuntu1
https://launchpad.net/ubuntu/+source/xz-utils/5.8.3-1ubuntu0.1
https://launchpad.net/ubuntu/+source/xz-utils/5.6.1+really5.4.5-1ubuntu0.4
https://launchpad.net/ubuntu/+source/xz-utils/5.2.5-2ubuntu1.2

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