In Das U-Boot versions 2016.11-rc1 through 2019.07-rc4, an underflow can cause memcpy() to overwrite a very large amount of data (including the whole stack) while reading a crafted ext4 filesystem.
https://lists.denx.de/pipermail/u-boot/2019-July/375514.html
https://github.com/u-boot/u-boot/commits/master
https://gist.github.com/deephooloovoo/d91b81a1674b4750e662dfae93804d75
http://lists.opensuse.org/opensuse-security-announce/2019-10/msg00004.html
http://lists.opensuse.org/opensuse-security-announce/2019-10/msg00002.html