USN-5013-1 fixed several vulnerabilities in systemd. This update provides the corresponding update for Ubuntu 16.04 ESM.
Original advisory details:
It was discovered that systemd incorrectly handled certain mount paths. A local attacker could possibly use this issue to cause systemd to crash, resulting in a denial of service. (CVE-2021-33910)
Mitchell Frank discovered that systemd incorrectly handled DHCP FORCERENEW packets. A remote attacker could possibly use this issue to reconfigure servers. (CVE-2020-13529)
{
    "availability": "Available with Ubuntu Pro (Infra-only): https://ubuntu.com/pro",
    "binaries": [
        {
            "binary_name": "libnss-myhostname",
            "binary_version": "229-4ubuntu21.31+esm1"
        },
        {
            "binary_name": "libnss-mymachines",
            "binary_version": "229-4ubuntu21.31+esm1"
        },
        {
            "binary_name": "libnss-resolve",
            "binary_version": "229-4ubuntu21.31+esm1"
        },
        {
            "binary_name": "libpam-systemd",
            "binary_version": "229-4ubuntu21.31+esm1"
        },
        {
            "binary_name": "libsystemd-dev",
            "binary_version": "229-4ubuntu21.31+esm1"
        },
        {
            "binary_name": "libsystemd0",
            "binary_version": "229-4ubuntu21.31+esm1"
        },
        {
            "binary_name": "libudev-dev",
            "binary_version": "229-4ubuntu21.31+esm1"
        },
        {
            "binary_name": "libudev1",
            "binary_version": "229-4ubuntu21.31+esm1"
        },
        {
            "binary_name": "systemd",
            "binary_version": "229-4ubuntu21.31+esm1"
        },
        {
            "binary_name": "systemd-container",
            "binary_version": "229-4ubuntu21.31+esm1"
        },
        {
            "binary_name": "systemd-coredump",
            "binary_version": "229-4ubuntu21.31+esm1"
        },
        {
            "binary_name": "systemd-journal-remote",
            "binary_version": "229-4ubuntu21.31+esm1"
        },
        {
            "binary_name": "systemd-sysv",
            "binary_version": "229-4ubuntu21.31+esm1"
        },
        {
            "binary_name": "udev",
            "binary_version": "229-4ubuntu21.31+esm1"
        }
    ]
}
          {
    "cves": [
        {
            "id": "CVE-2020-13529",
            "severity": [
                {
                    "type": "CVSS_V3",
                    "score": "CVSS:3.0/AV:A/AC:H/PR:N/UI:N/S:C/C:N/I:N/A:H"
                },
                {
                    "type": "CVSS_V3",
                    "score": "CVSS:3.1/AV:A/AC:H/PR:N/UI:N/S:C/C:N/I:N/A:H"
                },
                {
                    "type": "Ubuntu",
                    "score": "low"
                }
            ]
        },
        {
            "id": "CVE-2021-33910",
            "severity": [
                {
                    "type": "CVSS_V3",
                    "score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H"
                },
                {
                    "type": "CVSS_V3",
                    "score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H"
                },
                {
                    "type": "Ubuntu",
                    "score": "high"
                }
            ]
        }
    ],
    "ecosystem": "Ubuntu:Pro:16.04:LTS"
}