Gfilui

I have downloaded Viber and installed it via terminal to my Ubuntu 14.04 OS. For the installation I have used dpkg -i to install and apt-get install -f to install the dependencies:

wget -O viber.deb http://download.cdn.viber.com/cdn/desktop/Linux/viber.deb 
sudo dpkg -i viber.deb
sudo apt-get install -f

Although Viber is installed, it cannot be launched. Executing it via the terminal, I get the output bellow:

$ /opt/viber/Viber
./Viber: /usr/lib/x86_64-linux-gnu/libstdc++.so.6: version `GLIBCXX_3.4.20' not found (required by ./Viber)
./Viber: /usr/lib/x86_64-linux-gnu/libstdc++.so.6: version `CXXABI_1.3.8' not found (required by ./Viber)
./Viber: /usr/lib/x86_64-linux-gnu/libstdc++.so.6: version `CXXABI_1.3.8' not found (required by /opt/viber/lib/libQt5Location.so.5)
./Viber: /usr/lib/x86_64-linux-gnu/libstdc++.so.6: version `CXXABI_1.3.8' not found (required by /opt/viber/lib/libicui18n.so.52)
./Viber: /usr/lib/x86_64-linux-gnu/libstdc++.so.6: version `CXXABI_1.3.8' not found (required by /opt/viber/lib/libicuuc.so.52)
./Viber: /usr/lib/x86_64-linux-gnu/libstdc++.so.6: version `GLIBCXX_3.4.20' not found (required by /opt/viber/lib/libQt5WebEngineCore.so.5)
./Viber: /usr/lib/x86_64-linux-gnu/libstdc++.so.6: version `GLIBCXX_3.4.20' not found (required by /opt/viber/lib/libQt5Qml.so.5)
./Viber: /usr/lib/x86_64-linux-gnu/libstdc++.so.6: version `CXXABI_1.3.8' not found (required by /opt/viber/lib/libQt5Core.so.5)

I guess it has something to do with having an older version of some dependencies than required. The OS is up to date though. How can I fix this?

I suggest to install previous version - 4.2.2.6. I found it on the archive site.

Its MD5 is 4dec3ade37a3738c6f084858a4554861, so it does not modified.

Then install it as you did before:

sudo dpkg -i viber-for-linux-4-2-2-6-en-ubu.deb
sudo apt-get install -f

On my 14.04 LTS it launches normally.

Update: I got latest Viber 7.0.0.1035 working on my 14.04 LTS after manual downloading of libstdc++ from Xenial (16.04 LTS) to /opt/viber/lib directory:

wget -O viber.deb http://download.cdn.viber.com/cdn/desktop/Linux/viber.deb
sudo dpkg -i viber.deb
sudo apt-get install -f

wget http://mirrors.kernel.org/ubuntu/pool/main/g/gcc-5/libstdc++6_5.4.0-6ubuntu1~16.04.5_amd64.deb
dpkg -x libstdc++6_5.4.0-6ubuntu1~16.04.5_amd64.deb /tmp/stdc
sudo cp /tmp/stdc/usr/lib/x86_64-linux-gnu/libstdc++.so.6* /opt/viber/lib

sudo apt-get install libqt5gui5 # prevent errors about xcb

Try the following

sudo add-apt-repository ppa:ubuntu-toolchain-r/test
sudo apt update
sudo apt install gcc-4.9
sudo apt install libstdc++6

I think the above programs are not installed properly.