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[USN-8560-1] libXfont vulnerabilities

Posted on 20 July 2026
Ubuntu Security

==========================================================================Ubuntu Security Notice USN-8560-1
July 20, 2026

libxfont vulnerabilities
==========================================================================
A security issue affects these releases of Ubuntu and its derivatives:

- 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:

Several security issues were fixed in libXfont.

Software Description:
- libxfont: X11 font rasterisation library

Details:

It was discovered that libXfont incorrectly handled scaling bitmap
fonts, leading to a heap buffer overflow. An attacker able to access
the X server could use this issue to cause libXfont to crash,
resulting in a denial of service, or possibly execute arbitrary code.
(CVE-2026-56001)

It was discovered that libXfont did not properly check glyph bounds
when reading PCF fonts, leading to a heap buffer overflow. An
authenticated X client could use this issue to cause libXfont to
crash, resulting in a denial of service, or possibly execute arbitrary
code. (CVE-2026-56002)

It was discovered that libXfont did not properly check the size of the
property buffer when parsing PCF fonts, leading to a heap buffer
overflow. An authenticated X client could use this issue to cause
libXfont to crash, resulting in a denial of service, or possibly
execute arbitrary code. (CVE-2026-56003)

Update instructions:

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

Ubuntu 26.04 LTS
libxfont2 1:2.0.6-2ubuntu0.2

Ubuntu 24.04 LTS
libxfont2 1:2.0.6-1+deb13u1build0.24.04.2

Ubuntu 22.04 LTS
libxfont2 1:2.0.5-1ubuntu0.2

Ubuntu 20.04 LTS
libxfont2 1:2.0.3-1ubuntu0.20.04.1~esm2
Available with Ubuntu Pro

Ubuntu 18.04 LTS
libxfont2 1:2.0.3-1ubuntu0.1~esm2
Available with Ubuntu Pro

Ubuntu 16.04 LTS
libxfont1 1:1.5.1-1ubuntu0.16.04.4+esm2
Available with Ubuntu Pro

Ubuntu 14.04 LTS
libxfont1 1:1.4.7-1ubuntu0.4+esm2
Available with Ubuntu Pro

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

References:
https://ubuntu.com/security/notices/USN-8560-1
CVE-2017-16611, CVE-2026-56001, CVE-2026-56002, CVE-2026-56003

Package Information:
https://launchpad.net/ubuntu/+source/libxfont/1:2.0.6-2ubuntu0.2
https://launchpad.net/ubuntu/+source/libxfont/1:2.0.6-1+deb13u1build0.24.04.2
https://launchpad.net/ubuntu/+source/libxfont/1:2.0.5-1ubuntu0.2

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