Microsoft SharePoint Remote Code Execution Vulnerability

According to the CVSS metric, the attack complexity is high (AC:H). What does that mean for this vulnerability?
Successful exploitation of this vulnerability requires an attacker to prepare the target environment to improve exploit reliability.

According to the CVSS metric, the attack vector is local (AV:L). Why does the CVE title indicate that this is a remote code execution?
The word Remote in the title refers to the location of the attacker. This type of exploit is sometimes referred to as Arbitrary Code Execution (ACE). The attack itself is carried out locally. This means an attacker or victim needs to execute code from the local machine to exploit the vulnerability.

There are multiple update packages available for some of the affected software. Do I need to install all the updates listed in the Security Updates table for the software?
Yes. Customers should apply all updates offered for the software installed on their systems. If multiple updates apply, they can be installed in any order.

Security updates
16.0.5478.1000 — https://support.microsoft.com/help/5002659
16.0.5478.1000 — https://support.microsoft.com/help/5002544
16.0.10416.20026 — https://support.microsoft.com/help/5002657
16.0.10416.20026 — https://support.microsoft.com/help/5002664
16.0.17928.20290 — https://support.microsoft.com/help/5002658