An elevation of privilege vulnerability exists in Microsoft Exchange Server, aka "Microsoft Exchange Server Elevation of Privilege Vulnerability." This affects Microsoft Exchange Server.

CVE-2018-8581

An elevation of privilege vulnerability exists in Microsoft Exchange Server. An attacker who successfully exploited this vulnerability could attempt to impersonate any other user of the Exchange server.

To exploit the vulnerability, an attacker would need to execute a man-in-the-middle attack to forward an authentication request to a Microsoft Exchange Server, thereby allowing impersonation of another Exchange user.

To address this vulnerability, a registry value which enables NTLM authentication on the network loopback adapter needs to be removed. Future cumulative updates will ensure that this registry setting is configured correctly during installation of the cumulative update.


A registry value DisableLoopbackCheck exists under the registry key HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Lsa. The vulnerability described by CVE-2018-8581 is unexploitable if the DisableLoopbackCheck registry value is removed.

To remove the registry value, type the following command in an elevated CMD window:

reg delete HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Lsa /v DisableLoopbackCheck /f

Neither a restart of the operating system nor the Exchange Server is required after the removal of this registry value.

Note: It is important to remove only the DisableLoopbackCheck value. Care should be taken to not remove the Lsa key.

An elevation of privilege vulnerability exists in Microsoft Exchange Server. An attacker who successfully exploited this vulnerability could attempt to impersonate any other user of the Exchange server.
To exploit the vulnerability, an attacker would need to execute a man-in-the-middle attack to forward an authentication request to a Microsoft Exchange Server, thereby allowing impersonation of another Exchange user.
To address this vulnerability, a registry value which enables NTLM authentication on the network loopback adapter needs to be removed. Future cumulative updates will ensure that this registry setting is configured correctly during installation of the cumulative update.
A registry value DisableLoopbackCheck exists under the registry key HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Lsa. The vulnerability described by CVE-2018-8581 is unexploitable if the DisableLoopbackCheck registry value is removed.
To remove the registry value, type the following command in an elevated CMD window:
reg delete HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Lsa /v DisableLoopbackCheck /f
Neither a restart of the operating system nor the Exchange Server is required after the removal of this registry value.
Note: It is important to remove only the DisableLoopbackCheck value. Care should be taken to not remove the Lsa key.

Advisory: Microsoft Exchange Server Elevation of Privilege Vulnerability

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CVE-2018-8581

1 fix found:

Workaround

Advisory: Microsoft Exchange Server Elevation of Privilege Vulnerability