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AUSCERT External Security Bulletin Redistribution
tightvnc security update
23 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-2019-15681 CVE-2019-15680 CVE-2019-15679
CVE-2019-15678 CVE-2019-8287 CVE-2019-1568
CVE-2018-20748 CVE-2018-20022 CVE-2018-20021
CVE-2018-20020 CVE-2018-7225 CVE-2014-6053
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Package : tightvnc
Version : 1.3.9-6.5+deb8u1
CVE ID : CVE-2014-6053 CVE-2018-7225 CVE-2019-8287 CVE-2018-20021
CVE-2018-20022 CVE-2019-15678 CVE-2019-15679 CVE-2019-15680
Debian Bug : 945364
Several vulnerabilities have recently been discovered in TightVNC 1.x, an
X11 based VNC server/viewer application for Windows and Unix.
The rfbProcessClientNormalMessage function in rfbserver.c in TightVNC
server did not properly handle attempts to send a large amount of
ClientCutText data, which allowed remote attackers to cause a denial
of service (memory consumption or daemon crash) via a crafted message
that was processed by using a single unchecked malloc.
rfbProcessClientNormalMessage() in rfbserver.c did not sanitize
msg.cct.length, leading to access to uninitialized and potentially
sensitive data or possibly unspecified other impact (e.g., an integer
overflow) via specially crafted VNC packets.
TightVNC code contained global buffer overflow in HandleCoRREBBP
macro function, which could potentially have result in code
execution. This attack appeared to be exploitable via network
TightVNC in vncviewer/rfbproto.c contained a CWE-835: Infinite loop
vulnerability. The vulnerability allowed an attacker to consume
an excessive amount of resources like CPU and RAM.
TightVNC's vncviewer 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.
TightVNC code version contained heap buffer overflow in
rfbServerCutText handler, which could have potentially resulted in
code execution. This attack appeared to be exploitable via network
(partially aka CVE-2018-20748/libvnvserver)
TightVNC's vncviewer code contained a heap buffer overflow in
InitialiseRFBConnection function, which could have potentially
resulted in code execution. This attack appeared to be exploitable
via network connectivity.
(partially aka CVE-2018-20748/libvnvserver)
TightVNC's vncviewer code contained a null pointer dereference in
HandleZlibBPP function, which could have resulted in Denial of System
(DoS). This attack appeared to be exploitable via network
TightVNC contained a memory leak (CWE-655) in VNC server code, which
allowed an attacker to read stack memory and could have been abused
for information disclosure. Combined with another vulnerability, it
could have been used to leak stack memory and bypass ASLR. This
attack appeared to be exploitable via network connectivity.
For Debian 8 "Jessie", these problems have been fixed in version
We recommend that you upgrade your tightvnc 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
mike gabriel aka sunweaver (Debian Developer)
fon: +49 (1520) 1976 148
GnuPG Fingerprint: 9BFB AEE8 6C0A A5FF BF22 0782 9AF4 6B30 2577 1B31
mail: email@example.com, http://sunweavers.net
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