As told in the bug- report creating the symlinks in /usr/lib/firefox/ as a workaround did the trick, firefox is running again.
ln -s /usr/lib/x86_64-linux-gnu/libnssutil3.so
ln -s /usr/lib/x86_64-linux-gnu/libnss3.so
ln -s /usr/lib/x86_64-linux-gnu/libsmime3.so
ln -s /usr/lib/x86_64-linux-gnu/libssl3.so
thx