As a former security researcher, I am amazed that integer overflows are still a thing in 2018, in the Ruby core - so probably everywhere...
About 10 years ago, integer overflow vulnerabilities were trending in the security community. Plenty of nice vulnerabilities and exploits have been found with them - like in all PDF readers, ... I guess when the momentum of such vulnerabilities goes down, this class of bugs goes unnoticed.
Secure programming is hard, it's too bad we don't keep the learning we had in the past.