USN-8815-1: libass vulnerabilities

Publication date

24 September 2026

Overview

Several security issues were fixed in libass.


Packages

  • libass - Portable subtitle renderer for the ASS/SSA subtitle format

Details

It was discovered that libass incorrectly handled parsing operations for
specific nested character strings. An attacker could use this issue to
cause libass to crash, resulting in a denial of service, or possibly
execute arbitrary code. This issue only affected Ubuntu 14.04 LTS,
Ubuntu 16.04 LTS, Ubuntu 18.04 LTS and Ubuntu 20.04 LTS.
(CVE-2020-24994)

It was discovered that libass incorrectly handled certain outline
processing operations. An attacker could use this issue to cause libass
to crash, resulting in a denial of service. This issue only affected
Ubuntu 18.04 LTS and Ubuntu 20.04 LTS. (CVE-2020-26682)

It was discovered that libass incorrectly handled certain ASS subtitle
files when measuring wrapped lines. An attacker could use this issue to
cause libass to crash, resulting in a denial of service, or possibly
execute arbitrary code. This...

It was discovered that libass incorrectly handled parsing operations for
specific nested character strings. An attacker could use this issue to
cause libass to crash, resulting in a denial of service, or possibly
execute arbitrary code. This issue only affected Ubuntu 14.04 LTS,
Ubuntu 16.04 LTS, Ubuntu 18.04 LTS and Ubuntu 20.04 LTS.
(CVE-2020-24994)

It was discovered that libass incorrectly handled certain outline
processing operations. An attacker could use this issue to cause libass
to crash, resulting in a denial of service. This issue only affected
Ubuntu 18.04 LTS and Ubuntu 20.04 LTS. (CVE-2020-26682)

It was discovered that libass incorrectly handled certain ASS subtitle
files when measuring wrapped lines. An attacker could use this issue to
cause libass to crash, resulting in a denial of service, or possibly
execute arbitrary code. This issue only affected Ubuntu 24.04 LTS and
Ubuntu 26.04 LTS. (CVE-2026-61627)

It was discovered that libass incorrectly handled certain Matroska
subtitle chunks with negative ReadOrder values. An attacker could use
this issue to cause libass to crash, resulting in a denial of service,
or possibly execute arbitrary code. This issue only affected Ubuntu
26.04 LTS. (CVE-2026-61626)


Update instructions

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

Learn more about how to get the fixes.

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

Ubuntu Release Package Version
26.04 LTS resolute libass9 –  1:0.17.4-2ubuntu0.1~esm1  
24.04 LTS noble libass9 –  1:0.17.1-2ubuntu0.1~esm1  
20.04 LTS focal libass9 –  1:0.14.0-2ubuntu0.1~esm1  
18.04 LTS bionic libass9 –  1:0.14.0-1ubuntu0.1~esm1  
14.04 LTS trusty libass4 –  0.10.1-3ubuntu1+esm2  

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