Debian DLA-2016-1 : ssvnc security update

critical Nessus Plugin ID 131434


The remote Debian host is missing a security update.


Several vulnerabilities have been identified in the VNC code of ssvnc, an encryption-capable VNC client..

The vulnerabilities referenced below are issues that have originally been reported against Debian source package libvncserver (which also ships the libvncclient shared library). The ssvnc source package in Debian ships a custom-patched, stripped down and outdated variant of libvncclient, thus some of libvncclient's security fixes required porting over.


LibVNC contained heap out-of-bound write vulnerability inside structure in VNC client code that can result remote code execution


LibVNC contained a CWE-835: Infinite loop vulnerability in VNC client code. Vulnerability allows attacker to consume excessive amount of resources like CPU and RAM


LibVNC contained multiple weaknesses CWE-665: Improper Initialization vulnerability in VNC client code that allowed attackers to read stack memory and could be abused for information disclosure. Combined with another vulnerability, it could be used to leak stack memory layout and in bypassing ASLR.


LibVNC contained NULL pointer dereference in VNC client code that could result DoS.

For Debian 8 'Jessie', these problems have been fixed in version 1.0.29-2+deb8u1.

We recommend that you upgrade your ssvnc packages.

NOTE: Tenable Network Security has extracted the preceding description block directly from the DLA security advisory. Tenable has attempted to automatically clean and format it as much as possible without introducing additional issues.


Upgrade the affected ssvnc package.

See Also

Plugin Details

Severity: Critical

ID: 131434

File Name: debian_DLA-2016.nasl

Version: 1.4

Type: local

Agent: unix

Published: 12/3/2019

Updated: 1/11/2021

Supported Sensors: Frictionless Assessment Agent, Nessus Agent

Risk Information

CVSS Score Source: CVE-2018-20020


Risk Factor: Medium

Score: 5.9


Risk Factor: High

Base Score: 7.5

Temporal Score: 5.5

Vector: AV:N/AC:L/Au:N/C:P/I:P/A:P

Temporal Vector: E:U/RL:OF/RC:C


Risk Factor: Critical

Base Score: 9.8

Temporal Score: 8.5

Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Temporal Vector: E:U/RL:O/RC:C

Vulnerability Information

CPE: p-cpe:/a:debian:debian_linux:ssvnc, cpe:/o:debian:debian_linux:8.0

Required KB Items: Host/local_checks_enabled, Host/Debian/release, Host/Debian/dpkg-l

Exploit Ease: No known exploits are available

Patch Publication Date: 11/29/2019

Vulnerability Publication Date: 12/19/2018

Reference Information

CVE: CVE-2018-20020, CVE-2018-20021, CVE-2018-20022, CVE-2018-20024