CVE-2019-18684

DISPUTED Sudo through 1.8.29 allows local users to escalate to root
if they have write access to file descriptor 3 of the sudo process. This
occurs because of a race condition between determining a uid, and the
setresuid and openat system calls. The attacker can write “ALL ALL=(ALL)
NOPASSWD:ALL” to /proc/#####/fd/3 at a time when Sudo is prompting for a
password. NOTE: This has been disputed due to the way Linux /proc works. It
has been argued that writing to /proc/#####/fd/3 would only be viable if
you had permission to write to /etc/sudoers. Even with write permission to
/proc/#####/fd/3, it would not help you write to /etc/sudoers.

Notes