Windows Kerberos Elevation of Privilege Vulnerability

How could an attacker exploit this vulnerability?
An attacker who controls authentication in a trusted forest could send specially crafted authentication information to the target forest. Successful exploitation could raise the integrity level of the attacker's identity to System, allowing actions otherwise blocked by integrity-level restrictions where existing resource permissions already allow access. This does not grant SYSTEM-account privileges or target-forest administrator membership.

According to the CVSS metric, the attack complexity is high (AC:H). What does that mean for this vulnerability?
Successful exploitation requires an existing trust relationship between the attacker's forest and the target forest, together with resource permissions that already allow the attacker's identity access. The vulnerability bypasses integrity-level restrictions but does not grant otherwise absent resource access permissions.

Security updates
10.0.14393.9688 — https://support.microsoft.com/help/5131291
10.0.17763.9487 — https://support.microsoft.com/help/5131085
10.0.19044.7846 — https://support.microsoft.com/help/5131096
10.0.20348.5870 — https://support.microsoft.com/help/5131090
10.0.22631.7711 — https://support.microsoft.com/help/5131087
10.0.26100.9974 — https://support.microsoft.com/help/5132061
10.0.26100.9911 — https://support.microsoft.com/help/5132043
10.0.26100.33822 — https://support.microsoft.com/help/5131080
10.0.26100.33730 — https://support.microsoft.com/help/5131077
10.0.28000.3501 — https://support.microsoft.com/help/5132059