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V-93565

CAT II (Medium)

Windows Server 2019 Exploit Protection system-level mitigation, Randomize memory allocations (Bottom-Up ASLR), must be on.

Rule ID

SV-103651r1_rule

STIG

Windows Server 2019 Security Technical Implementation Guide

Version

V1R3

CCIs

CCI-002824

Discussion

Exploit protection enables mitigations against potential threats at the system and application level. Several mitigations, including "Randomize memory allocations (Bottom-Up ASLR)", are enabled by default at the system level. Bottom-Up ASLR (address space layout randomization) randomizes locations for virtual memory allocations, including those for system structures. If this is turned off, Windows may be subject to various exploits.

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This is applicable to unclassified systems, for other systems this is NA.

The default configuration in Exploit Protection is "On by default" which meets this requirement.  The PowerShell query results for this show as "NOTSET".

Run "Windows PowerShell" with elevated privileges (run as administrator).

Enter "Get-ProcessMitigation -System".

If the status of "ASLR: BottomUp" is "OFF", this is a finding.

Values that would not be a finding include:

ON
NOTSET (Default configuration)

Fix Text

Ensure Exploit Protection system-level mitigation, "Randomize memory allocations (Bottom-Up ASLR)" is turned on. The default configuration in Exploit Protection is "On by default" which meets this requirement.

Open "Windows Defender Security Center".

Select "App & browser control".

Select "Exploit protection settings".

Under "System settings", configure "Randomize memory allocations (Bottom-Up ASLR)" to "On by default" or "Use default (<On>)".   

The STIG package includes a DoD EP XML file in the "Supporting Files" folder for configuring application mitigations defined in the STIG.  This can also be modified to explicitly enforce the system level requirements.  Adding the following to the XML file will explicitly turn Bottom-Up ASLR on (other system level EP requirements can be combined under <SystemConfig>):

<SystemConfig>
  <ASLR BottomUp="true" HighEntropy="true"></ASLR>
</SystemConfig>

The XML file is applied with the group policy setting Computer Configuration >> Administrative Settings >> Windows Components >> Windows Defender Exploit Guard >> Exploit Protection >> "Use a common set of exploit protection settings" configured to "Enabled" with file name and location defined under "Options:". It is recommended the file be in a read-only network location.