==========================================================================
Ubuntu Security Notice USN-4434-1
July 23, 2020

libvncserver vulnerabilities
==========================================================================

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

– Ubuntu 20.04 LTS
– Ubuntu 18.04 LTS
– Ubuntu 16.04 LTS

Summary:

Several security issues were fixed in LibVNCServer.

Software Description:
– libvncserver: vnc server library

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 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:

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

Ubuntu 20.04 LTS:
libvncclient1 0.9.12+dfsg-9ubuntu0.2
libvncserver1 0.9.12+dfsg-9ubuntu0.2

Ubuntu 18.04 LTS:
libvncclient1 0.9.11+dfsg-1ubuntu1.3
libvncserver1 0.9.11+dfsg-1ubuntu1.3

Ubuntu 16.04 LTS:
libvncclient1 0.9.10+dfsg-3ubuntu0.16.04.5
libvncserver1 0.9.10+dfsg-3ubuntu0.16.04.5

After a standard system update you need to restart LibVNCServer
applications to make all the necessary changes.

References:
https://usn.ubuntu.com/4434-1
CVE-2019-20839, CVE-2019-20840, CVE-2020-14396, CVE-2020-14397,
CVE-2020-14398, CVE-2020-14399, CVE-2020-14400, CVE-2020-14401,
CVE-2020-14402, CVE-2020-14403, CVE-2020-14404, CVE-2020-14405

Package Information:
https://launchpad.net/ubuntu/+source/libvncserver/0.9.12+dfsg-9ubuntu0.2
https://launchpad.net/ubuntu/+source/libvncserver/0.9.11+dfsg-1ubuntu1.3
https://launchpad.net/ubuntu/+source/libvncserver/0.9.10+dfsg-3ubuntu0.16.04.5

—–BEGIN PGP SIGNATURE—–

iQEzBAEBCAAdFiEElnO/d49FoUPK9fwytGdj0GOh2+wFAl8Z/UAACgkQtGdj0GOh
2+wYYAgApNN6tlV7E7QN0b6r4sZlvCwmkzeSlOXxH16zb8CXnPRYQB9vuKUscz1O
CqIPxZSdWaL80ak2EJKO2hvVX6Qif1Uhbf25Yp2C10BVkkUeyKrL7jY1QamNtQoR
rpvMcFONy3I/hwiCcj9D/IlPXAPuuSMgsPErMGYQyRzBmSSksrg8FBlnGez+lRTy
y9bUgyZztIbTMgxJeiuKVy1PmR21KIsnMI1sYPP0nlFNo6unEHqUhB3a4bL4xU61
tHmuOMeeCwjCtFa8SeZaFP6IKbj0dFQjKH2iYwJ1FUywq2HTQo4sk4uOvJg/KPlt
55pnFJ1Lq+ss3Zd91rd+bFAxwsaB0g==
=HHgb
—–END PGP SIGNATURE—–
—