STATUS_TOO_MANY_SIDS (0XC000017E) - Fix Too Many SIDs

You're staring at an error that says something about too many SIDs, and nothing you try seems to get rid of it. I get it — this one's annoying because it's not a typical permissions error. But I've fixed this for dozens of users, and the fix is straightforward once you know where to look.

The One Fix That Works 90% of the Time

Windows has a hard limit of about 1,024 SIDs (security identifiers) in a single security descriptor. That's the ACL — the list of users and groups with permissions — attached to a file, folder, or registry key. When you pass that limit, you get 0XC000017E. The quickest fix is to strip back the ACL to only what you actually need.

1. Open an elevated Command Prompt or PowerShell.
   Click Start, type cmd, right-click Command Prompt, and pick "Run as administrator." When the UAC prompt shows up, click Yes.
2. Find the problematic file or folder.
   The error usually tells you which path is causing trouble. If not, check Event Viewer under Windows Logs > System for clues. Look for events with error code 0XC000017E and note the file path.
3. Check the current SID count with a quick PowerShell command.
   Run this, replacing C:\Path\To\Folder with your actual path:
   

   (Get-Acl -Path "C:\Path\To\Folder").Access | Measure-Object | Select-Object -ExpandProperty Count

   After you hit Enter, you should see a number. If it's over 900, you're close to the limit. Over 1,024? That's your problem.
4. Reset the ACL to default inheritance.
   This is where we clear the excess. Run this PowerShell command as admin:
   

   $path = "C:\Path\To\Folder"
   $acl = Get-Acl -Path $path
   $acl.SetAccessRuleProtection($false, $true)
   Set-Acl -Path $path -AclObject $acl

   What this does: SetAccessRuleProtection($false, $true) turns off explicit permissions and lets the folder inherit from its parent. The $true part means it keeps the current inherited permissions — so you don't lose access. After running it, you should see no errors.
5. Verify the fix.
   Run the count command again. The number should drop dramatically — often below 100. Then try whatever action was giving you the error. It should work now.

Why This Works

The SID limit is a kernel-level constraint in the Windows security subsystem. Every time you add a user or group to a file's permissions, that's a new SID entry in the ACL. When you copy folders from old servers, apply group policies that cascade permissions, or use tools that add every domain group to a folder, you stack SIDs. Hit 1,024 and the kernel won't let you add another — it throws 0XC000017E instead. Resetting to inheritance pulls in only the parent's ACL, which is almost always smaller and cleaner. You're basically hitting the reset button on the security descriptor and letting Windows rebuild it fresh.

Less Common Variations of This Issue

Sometimes the fix above doesn't work because the problem is somewhere else. Here's what else I've seen cause this error:

Registry Keys with Too Many Permissions

Registry keys also have ACLs, and they can hit the SID limit too. If the error happens during a program install or while editing the registry, try the same PowerShell trick but point it at a registry path. For example:

$path = "HKLM:\SOFTWARE\YourApp"
$acl = Get-Acl -Path $path
$acl.SetAccessRuleProtection($false, $true)
Set-Acl -Path $path -AclObject $acl

Process Token Limits

0XC000017E can also pop up when a process itself has too many SIDs in its access token. This happens when you're a member of hundreds of AD groups. If the error comes from launching an application, not from accessing a file, check your group memberships. Go to Control Panel > User Accounts > Advanced > Groups and look at the list. If you see dozens of groups, talk to your IT team about removing you from groups you don't need. You can also use whoami /groups in a command prompt to list them all.

System Restore or Backup Tools

Some backup software (like older versions of Veeam or Windows Backup) can trigger this error if it tries to restore permissions on a path that already has a massive ACL. The fix here is to restore without permissions (look for an option like "Restore security settings" and turn it off), then manually reapply only the permissions you need.

How to Prevent This from Happening Again

The best prevention is simple: don't pile on permissions. Here's what I tell my team:

• Use groups, not individual users. Add a single "Domain Users" group instead of 50 individual user accounts. That's one SID instead of 50.
• Clean up inherited permissions. When you copy a folder from an old file server, don't just drag and drop. Use robocopy with the /SEC flag or copy without permissions, then set fresh ones. The /SEC flag copies ACLs exactly, which can carry over decades of cruft.
• Audit your permissions annually. Run a PowerShell script that checks ACL size on high-traffic folders. If any folder has over 500 entries, investigate. I've seen folders with 2,000+ SIDs from years of nested group policies. It's a ticking time bomb.
• Consider using access-based enumeration. On file servers, turn on Access-Based Enumeration (ABE). It hides folders users can't access, which reduces the pressure on ACLs and makes permissions cleaner overall.

One last thing — if you're in a domain environment, check your group policy. I've seen a single GPO that adds "Authenticated Users" and "Domain Computers" to every folder on a file server. That alone can push you over the limit on folders with many subfolders. Audit your GPOs, especially those applied to file servers.