Snap! C++
Fast Websites: Powerful CMS for Apache written in C++
...The result is quite extensible as it offers a plug-in mechanism that everyone is welcome to use to create their own extensions.
Debian Packages can be downloaded from https://launchpad.net/~snapcpp -- you can find instructions there on how to add the PPA to your sources on your Ubuntu system and just use apt-get install / upgrade as required.