Joe Vennix discovered a stack-based buffer overflow vulnerability in sudo, a program designed to provide limited super user privileges to specific users, triggerable when configured with the pwfeedback option enabled. An unprivileged user can take advantage of this flaw to obtain full root privileges.
Details can be found in the upstream advisory at https://www.sudo.ws/alerts/pwfeedback.html .
For the oldstable distribution (stretch), this problem has been fixed in version 1.8.19p1-2.1+deb9u2.
For the stable distribution (buster), exploitation of the bug is prevented due to a change in EOF handling introduced in 1.8.26.
We recommend that you upgrade your sudo packages.
For the detailed security status of sudo please refer to its security tracker page at: https://security-tracker.debian.org/tracker/sudo