Microsoft Security Response Center

**According to the CVSS metric, privileges required is low (PR:L). What does that mean for this vulnerability?** Any authenticated attacker could trigger this vulnerability. It does not require admin or other elevated privileges.

**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. For example, when the score indicates that the **Attack Vector** is **Local** and **User Interaction** is **Required**, this could describe an exploit in which an attacker, through social engineering, convinces a victim to download and open a specially crafted file from a website which leads to a local attack on their computer.

**What privileges could be gained by an attacker who successfully exploited this vulnerability?** An attacker who successfully exploited this vulnerability could gain SYSTEM privileges.

**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.

**What can cause this vulnerability?** The vulnerability occurs due to improper validation of cmdlet arguments. **Does the attacker need to be in an authenticated role in the Exchange Server?** Yes, the attacker must be authenticated.

The following workarounds might be helpful in your situation. In all cases, Microsoft strongly recommends that you install the updates for this vulnerability as soon as possible even if you plan to leave either of these workarounds in place: **Disable the HTTP/2 protocol on your web server by using the Registry Editor** **Note** Using Registry Editor incorrectly can cause serious problems that may require you to reinstall your operating system. Microsoft cannot guarantee that problems resulting from the incorrect use of Registry Editor can be solved. Use Registry Editor at your own risk. For information about how to edit the registry, view the "Changing Keys and Values" Help topic in Registry Editor (Regedit.exe) or view the "Add and Delete Information in the Registry" and "Edit Registry Data" Help topics in Regedt32.exe. 1. Click **Start**, click **Run**, type **Regedit** in the **Open** box, and then click **OK**. 2. Locate and then click the following registry subkey: HKLM\SYST...

**What privileges could be gained by an attacker who successfully exploited this vulnerability?** An attacker who successfully exploited this vulnerability could gain SYSTEM privileges.

**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.

**The following mitigating factors might be helpful in your situation:** Exploitation of this vulnerability requires an attacker to trick or convince the victim into connecting to their malicious server. If your environment only connects to known, trusted servers and there is no ability to reconfigure existing connections to point to another location (for example you use TLS encryption with certificate validation), the vulnerability cannot be exploited.

**How could an attacker exploit this vulnerability?** An attacker could exploit this path traversal vulnerability by leveraging the OcsPowershell endpoint within Skype for Business Server 2019 CU7 Hotfix 2 and Skype for Business Server 2015 CU13 Hotfix 1. Exploitation of this vulnerability requires the authenticated remote user be granted either the CsVoiceAdministrator or CsServerAdministrator role in order to create arbitrary files on the server. This exploit would allow the attacker to execute arbitrary code on the server.