This challenge has no (intended) bug. Please solve it anyway. https://mdsattacks.com might be helpful. It's running on GCE on a skylake with 2vCPUs.

https://storage.googleapis.com/gctf-2019-attachments/c9fd59af35777bb8f2eb3965741b898261b7303670efedfb1d38696398278946 sandbox-ridl.ctfcompetition.com 1337