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23 December 2019

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             AUSCERT External Security Bulletin Redistribution

                         tightvnc security update
                             23 December 2019


        AusCERT Security Bulletin Summary

Product:           tightvnc
Publisher:         Debian
Operating System:  Debian GNU/Linux 8
Impact/Access:     Execute Arbitrary Code/Commands -- Remote/Unauthenticated
                   Denial of Service               -- Remote/Unauthenticated
                   Access Confidential Data        -- Remote/Unauthenticated
Resolution:        Patch/Upgrade
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

Reference:         ESB-2019.4520

Original Bulletin: 

- --------------------------BEGIN INCLUDED TEXT--------------------

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

    (aka CVE-2018-20020/libvncserver)


    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

- --=20

mike gabriel aka sunweaver (Debian Developer)
fon: +49 (1520) 1976 148

GnuPG Fingerprint: 9BFB AEE8 6C0A A5FF BF22  0782 9AF4 6B30 2577 1B31
mail: sunweaver@debian.org, http://sunweavers.net

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