Coverity isn't useless. It finds these kinds of buffer overflow errors easily. It's shameful that a prominent keystone FOSS project is using such outdated coding practices in the first place. Not using the free tooling available for such projects is doubly so.
Systemd uses Simmle LGTM and QL for static code analysis which is a good thing since Coverty Scan is currently down without an ETA for restoration.
the flaws have existed for years.
As proven by a large majority of C developers ignoring lint since 1979.