De acordo com madison a menos que você esteja usando old-stable (wheezy), você deve ter a versão 4.3. Você também pode ativar os repositórios wheezy-backports .
virtualbox | 4.1.18-dfsg-2+deb7u5 | wheezy | source, amd64, i386
virtualbox | 4.1.42-dfsg-1+deb7u1~bpo60+1 | squeeze-backports | source, amd64, i386
virtualbox | 4.1.42-dfsg-1+deb7u1 | wheezy-p-u | source, amd64, i386
virtualbox | 4.1.42-dfsg-1+deb7u1 | wheezy-security | source, amd64, i386
virtualbox | 4.3.18-dfsg-3 | jessie-kfreebsd/contrib | source
virtualbox | 4.3.18-dfsg-3+deb8u3 | jessie/contrib | source, amd64, i386
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virtualbox | 4.3.32-dfsg-1+deb8u2~bpo70+1 | wheezy-backports/contrib | source, amd64, i386
=======================================================================
virtualbox | 4.3.32-dfsg-1+deb8u2 | jessie-kfreebsd-security/contrib | source
virtualbox | 4.3.32-dfsg-1+deb8u2 | jessie-p-u/contrib | source, amd64, i386
virtualbox | 4.3.32-dfsg-1+deb8u2 | jessie-security/contrib | source, amd64, i386
virtualbox | 5.0.10-dfsg-7~bpo8+1 | jessie-backports/contrib | source, amd64, i386
virtualbox | 5.0.12-dfsg-1 | stretch/contrib | source, amd64, i386
virtualbox | 5.0.12-dfsg-2 | sid/contrib | source, amd64, i386