clamav vulnerabilities

USN-4918-1 fixed several vulnerabilities in ClamAV. This update provides
the corresponding update for Ubuntu 14.04 ESM.
Original advisory details:

It was discovered that ClamAV incorrectly handled parsing Excel documents.
A remote attacker could possibly use this issue to cause ClamAV to hang,
resulting in a denial of service. (CVE-2021-1252)

It was discovered that ClamAV incorrectly handled parsing PDF documents. A
remote attacker could possibly use this issue to cause ClamAV to crash,
resulting in a denial of service. (CVE-2021-1404)

It was discovered that ClamAV incorrectly handled parsing email. A remote
attacker could possibly use this issue to cause ClamAV to crash, resulting
in a denial of service. (CVE-2021-1405)