1. Ubuntu Security Notices
  2. USN-4434-1

USN-4434-1: LibVNCServer vulnerabilities

Publication date

23 July 2020

Overview

Several security issues were fixed in LibVNCServer.

Releases

Packages

Details

Ramin Farajpour Cami discovered that LibVNCServer incorrectly handled
certain malformed unix socket names. A remote attacker could exploit this
with a crafted socket name, leading to a denial of service, or possibly
execute arbitrary code. (CVE-2019-20839)

It was discovered that LibVNCServer did not properly access byte-aligned
data. A remote attacker could possibly use this issue to cause
LibVNCServer to crash, resulting in a denial of service. This issue only
affected Ubuntu 18.04 LTS and Ubuntu 16.04 LTS. (CVE-2019-20840)

Christian Beier discovered that LibVNCServer incorrectly handled anonymous
TLS connections. A remote attacker could possibly use this issue to cause
LibVNCServer to crash, resulting in a denial of service. This issue only
affected Ubuntu 20.04 LTS. (CVE-2020-14396)

It was discovered that...

Ramin Farajpour Cami discovered that LibVNCServer incorrectly handled
certain malformed unix socket names. A remote attacker could exploit this
with a crafted socket name, leading to a denial of service, or possibly
execute arbitrary code. (CVE-2019-20839)

It was discovered that LibVNCServer did not properly access byte-aligned
data. A remote attacker could possibly use this issue to cause
LibVNCServer to crash, resulting in a denial of service. This issue only
affected Ubuntu 18.04 LTS and Ubuntu 16.04 LTS. (CVE-2019-20840)

Christian Beier discovered that LibVNCServer incorrectly handled anonymous
TLS connections. A remote attacker could possibly use this issue to cause
LibVNCServer to crash, resulting in a denial of service. This issue only
affected Ubuntu 20.04 LTS. (CVE-2020-14396)

It was discovered that LibVNCServer incorrectly handled region clipping. A
remote attacker could possibly use this issue to cause LibVNCServer to
crash, resulting in a denial of service. (CVE-2020-14397)

It was discovered that LibVNCServer did not properly reset incorrectly
terminated TCP connections. A remote attacker could possibly use this
issue to cause an infinite loop, resulting in a denial of service.
(CVE-2020-14398)

It was discovered that LibVNCServer did not properly access byte-aligned
data. A remote attacker could possibly use this issue to cause
LibVNCServer to crash, resulting in a denial of service. (CVE-2020-14399,
CVE-2020-14400)

It was discovered that LibVNCServer incorrectly handled screen scaling on
the server side. A remote attacker could use this issue to cause
LibVNCServer to crash, resulting in a denial of service, or possibly
execute arbitrary code. (CVE-2020-14401)

It was discovered that LibVNCServer incorrectly handled encodings. A
remote attacker could use this issue to cause LibVNCServer to crash,
resulting in a denial of service, or possibly execute arbitrary code.
(CVE-2020-14402, CVE-2020-14403, CVE-2020-14404)

It was discovered that LibVNCServer incorrectly handled TextChat messages.
A remote attacker could possibly use this issue to cause LibVNCServer to
crash, resulting in a denial of service. (CVE-2020-14405)

Update instructions

After a standard system update you need to restart LibVNCServer applications to 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
20.04 focal libvncclient1 –  0.9.12+dfsg-9ubuntu0.2
libvncserver1 –  0.9.12+dfsg-9ubuntu0.2
18.04 bionic libvncclient1 –  0.9.11+dfsg-1ubuntu1.3
libvncserver1 –  0.9.11+dfsg-1ubuntu1.3
16.04 xenial libvncclient1 –  0.9.10+dfsg-3ubuntu0.16.04.5
libvncserver1 –  0.9.10+dfsg-3ubuntu0.16.04.5

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References

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