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Ubuntu libXfont Important Denial Of Service Heap Overflow Vuln 8560-1

ubuntu
Calendar Grey July 20, 2026
Scroller Ubuntu
Explore the critical updates for libXfont addressing denial of service issues and buffer overflows impacting various Ubuntu versions.
Several security issues were fixed in libXfont.

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...

Read the Full Advisory

Topics%20covered

Topics Covered

security advisory denial of service Ubuntu important heap overflow libxfont

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

Severity
important
Lowest
Low
Medium
High
Critical

Ubuntu Security Notice USN-8560-1

Topics%20covered

Topics Covered

security advisory denial of service Ubuntu important heap overflow libxfont

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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