Windows Telephony Service Elevation of Privilege Vulnerability

What privileges could be gained by an attacker who successfully exploited the vulnerability?
An attacker could use this vulnerability to elevate privileges from Medium Integrity Level to Local Service.

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 win a race condition.

Security updates
10.0.17763.9121 — https://support.microsoft.com/help/5120238
10.0.20348.5499 — https://support.microsoft.com/help/5120242
10.0.20348.5440 — https://support.microsoft.com/help/5120229
10.0.19044.7663 — https://support.microsoft.com/help/5120249
10.0.26100.33296 — https://support.microsoft.com/help/5120233
10.0.26100.33222 — https://support.microsoft.com/help/5120228
10.0.26200.9168 — https://support.microsoft.com/help/5121003
10.0.26200.9106 — https://support.microsoft.com/help/5120994
10.0.22631.7517 — https://support.microsoft.com/help/5120240
10.0.28000.2704 — https://support.microsoft.com/help/5121000
10.0.14393.9418 — https://support.microsoft.com/help/5120418
6.2.9200.26280 — https://support.microsoft.com/help/5120386
6.3.9600.23338 — https://support.microsoft.com/help/5120385