==========================================================================
Ubuntu Security Notice USN-4991-1
June 17, 2021

libxml2 vulnerabilities
==========================================================================

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

- Ubuntu 21.04
- Ubuntu 20.10
- Ubuntu 20.04 LTS
- Ubuntu 18.04 LTS
- Ubuntu 16.04 ESM
- Ubuntu 14.04 ESM

Summary:

Several security issues were fixed in libxml2.

Software Description:
- libxml2: GNOME XML library

Details:

Yunho Kim discovered that libxml2 incorrectly handled certain error
conditions. A remote attacker could exploit this with a crafted XML file to
cause a denial of service, or possibly cause libxml2 to expose sensitive
information. This issue only affected Ubuntu 14.04 ESM, and Ubuntu 16.04
ESM. (CVE-2017-8872)

Zhipeng Xie discovered that libxml2 incorrectly handled certain XML
schemas. A remote attacker could possibly use this issue to cause a denial
of service. This issue only affected Ubuntu 14.04 ESM, Ubuntu 16.04 ESM,
and Ubuntu 18.04 LTS. (CVE-2019-20388)

It was discovered that libxml2 incorrectly handled invalid UTF-8 input. A
remote attacker could possibly exploit this with a crafted XML file to
cause libxml2 to crash, resulting in a denial of service. This issue only
affected Ubuntu 14.04 ESM, Ubuntu 16.04 ESM, Ubuntu 18.04 LTS, Ubuntu 20.04
LTS and Ubuntu 20.10. (CVE-2020-24977)

It was discovered that libxml2 incorrectly handled invalid UTF-8 input. A
remote attacker could possibly exploit this with a crafted XML file to
cause libxml2 to crash, resulting in a denial of service. (CVE-2021-3517)

It was discovered that libxml2 did not properly handle certain crafted XML
files. A local attacker could exploit this with a crafted input to cause
libxml2 to crash, resulting in a denial of service, or possibly execute
arbitrary code. (CVE-2021-3516, CVE-2021-3518)

It was discovered that libxml2 incorrectly handled error states. A remote
attacker could exploit this with a crafted XML file to cause libxml2 to
crash, resulting in a denial of service. (CVE-2021-3537)

Sebastian Pipping discovered that libxml2 did not properly handle certain
crafted XML files. A remote attacker could exploit this with a crafted XML
file to cause libxml2 to crash, resulting in a denial of service. This
issue only affected Ubuntu 20.04 LTS, Ubuntu 20.10, and Ubuntu 21.04.
(CVE-2021-3541)

Update instructions:

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

Ubuntu 21.04:
  libxml2                         2.9.10+dfsg-6.3ubuntu0.1
  libxml2-utils                   2.9.10+dfsg-6.3ubuntu0.1

Ubuntu 20.10:
  libxml2                         2.9.10+dfsg-5ubuntu0.20.10.2
  libxml2-utils                   2.9.10+dfsg-5ubuntu0.20.10.2

Ubuntu 20.04 LTS:
  libxml2                         2.9.10+dfsg-5ubuntu0.20.04.1
  libxml2-utils                   2.9.10+dfsg-5ubuntu0.20.04.1

Ubuntu 18.04 LTS:
  libxml2                         2.9.4+dfsg1-6.1ubuntu1.4
  libxml2-utils                   2.9.4+dfsg1-6.1ubuntu1.4

Ubuntu 16.04 ESM:
  libxml2                         2.9.3+dfsg1-1ubuntu0.7+esm1
  libxml2-utils                   2.9.3+dfsg1-1ubuntu0.7+esm1

Ubuntu 14.04 ESM:
  libxml2                         2.9.1+dfsg1-3ubuntu4.13+esm2
  libxml2-utils                   2.9.1+dfsg1-3ubuntu4.13+esm2

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

References:
  https://ubuntu.com/security/notices/USN-4991-1
  CVE-2017-8872, CVE-2019-20388, CVE-2020-24977, CVE-2021-3516,
  CVE-2021-3517, CVE-2021-3518, CVE-2021-3537, CVE-2021-3541

Package Information:
  https://launchpad.net/ubuntu/+source/libxml2/2.9.10+dfsg-6.3ubuntu0.1
  https://launchpad.net/ubuntu/+source/libxml2/2.9.10+dfsg-5ubuntu0.20.10.2
  https://launchpad.net/ubuntu/+source/libxml2/2.9.10+dfsg-5ubuntu0.20.04.1
  https://launchpad.net/ubuntu/+source/libxml2/2.9.4+dfsg1-6.1ubuntu1.4