https://nvd.nist.gov/vuln/detail/CVE-2017-15908 says this is a infinite loop DoS in systemd-resolved, so it can't be the (hypothetical) bug described by the GP since it's neither a RCE nor in systemd PID1.
Possibly the IPv6 packet one, CVE-2018-15688? [0] A basic buffer overflow in systemd meant oversized network packets could be used for DoS or "potential code execution".