Linux kernel ext4 filesystem is vulnerable to an out-of-bound access in the ext4_ext_drop_refs() function when operating on a crafted ext4 filesystem image.
https://usn.ubuntu.com/3871-5/
https://usn.ubuntu.com/3871-4/
https://usn.ubuntu.com/3871-3/
https://usn.ubuntu.com/3871-1/
https://usn.ubuntu.com/3754-1/
https://usn.ubuntu.com/3753-2/
https://usn.ubuntu.com/3753-1/
https://lists.debian.org/debian-lts-announce/2018/07/msg00020.html