Linux Security
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    Ubuntu 4434-1: LibVNCServer vulnerabilities

    Date
    202
    Posted By
    Several security issues were fixed in LibVNCServer.
    ==========================================================================
    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
    
    
    

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