hi, any oklder than 5.2 will faild to build the kernel module again linux 4.7+ and in jessie/*stretch* there are kernels 4.7+ (4.9+ for backports and 4.15+)
please remove it the virtualbox backport until a good package are available.. also i can see that strecht not have a virtualbox normal package.. *i think a debian release cannot be do if many important package are not available due broke upgrades!* an upgrade from jessie to strecht broke the setup of a virtualbox user! Lenz McKAY Gerardo (PICCORO) http://qgqlochekone.blogspot.com