KB5007651 is the Windows Defender (Microsoft Defender Antivirus) platform update. The behavior described (repeated re‑offer, install stalling, no clear error) is consistent with a servicing issue in the Windows Server 2025 update chain rather than something that can be reliably fixed by registry edits on a sysprep image.
From the available information, the supported way to stabilize Windows Server 2025 update behavior is to ensure the image is on a later cumulative update where known servicing issues are resolved, rather than trying to suppress or hack around a specific Defender platform package.
Specifically:
- Install a newer cumulative update on the image
- Install a cumulative update released on or after November 11, 2025 (for example, KB5068861 or later). These builds include fixes that remove the need for Known Issue Rollback (KIR) workarounds and address earlier update issues.
- For even newer builds, install a 2026 cumulative update such as KB5075899 (OS Build 26100.32370) on the image. Microsoft now ships the latest Servicing Stack Update (SSU) together with the Latest Cumulative Update (LCU), so applying the latest LCU also refreshes the servicing stack.
- Use Windows Update / Windows Update for Business on the reference VM and let it reach the latest available build (for example, 26100.32370 or later) before running sysprep.
- Let Windows Update handle Defender platform updates
- Do not attempt to permanently block or remove KB5007651 in the registry or file system on the image. Defender platform updates are serviced as part of the OS security stack and are expected to re‑offer until the platform is at the required baseline for the installed OS build.
- Once the OS is on a current cumulative update with the integrated SSU, repeated re‑offers of older Defender platform packages typically stop because the newer LCU supersedes or correctly registers the Defender platform state.
- If the image is on a pre‑November‑2025 build
- If using a build earlier than the November 11, 2025 cumulative update, and there are known issues affecting update applicability, apply the special Known Issue Rollback (KIR) Group Policy for Windows Server 2025, then reboot, and re‑run Windows Update before capturing the image. This ensures the update stack is in a supported state.
- Capture the image only after updates are stable
- After installing a current cumulative update and letting Windows Update complete (no pending restarts, no repeated offers of the same Defender platform update), run sysprep and capture the image.
- Avoid capturing while a specific update (like KB5007651) is in a partially installed or repeatedly failing state, as that behavior can be baked into all deployed servers.
There is no supported registry or file‑level “permanent” block for KB5007651 on Server 2025 that would be preferable to moving the image to a newer, fixed cumulative update and letting the Defender platform be serviced normally.
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