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AUSCERT External Security Bulletin Redistribution
ssvnc security update
2 December 2019
AusCERT Security Bulletin Summary
Operating System: Debian GNU/Linux 8
Impact/Access: Execute Arbitrary Code/Commands -- Remote/Unauthenticated
Denial of Service -- Remote/Unauthenticated
Access Confidential Data -- Remote/Unauthenticated
CVE Names: CVE-2018-20024 CVE-2018-20022 CVE-2018-20021
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Package : ssvnc
Version : 1.0.29-2+deb8u1
CVE ID : CVE-2018-20020 CVE-2018-20021 CVE-2018-20022 CVE-2018-20024
Debian Bug : 945827
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custom-patched, stripped down and outdated variant of libvncclient, thus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
We recommend that you upgrade your ssvnc packages.
Further information about Debian LTS security advisories, how to apply
these updates to your system and frequently asked questions can be
found at: https://wiki.debian.org/LTS
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