Latest Win 11 updates have enforced SID and now I am having issues with duplicate SIDs

If you are experiencing NTLM authentication failures due to duplicate machine SIDs in a workgroup environment, it is important to understand that Microsoft has stated that cloning systems can lead to duplicate SIDs, which can cause significant issues in such environments. Unfortunately, the context provided does not include specific temporary Group Policy mitigations for this issue.

To resolve authentication failures related to duplicate SIDs, the best course of action is to ensure that each machine has a unique SID. This can be achieved by re-installing the operating system on the affected machines or using tools like NewSID to generate new SIDs. However, Microsoft supports cloning only in very limited scenarios, primarily before the GUI portion of Windows Setup has been reached.

For further assistance, consider reaching out to Microsoft support for guidance tailored to your specific situation regarding the NTLM authentication failures and duplicate SIDs.

References:

• NewSID v4.10

Hello Jonathan Grevenow

This issue is linked to duplicate machine SIDs, which can cause authentication problems across systems. To apply it, you’ll need to configure the “Network security: Restrict NTLM” settings in Group Policy to allow NTLM in your environment until you can remediate the duplicate SIDs. Please note that this mitigation is intended as a short‑term workaround, and the recommended long‑term solution is to regenerate unique SIDs for affected machines or move them into a domain environment where SID uniqueness is enforced.

I hope this helps you stabilize your environment. If you find this answer helpful, please don’t forget to click “Accept Answer” 🙂.

Harry.