Microsoft Warns Most Windows Devices May Face Boot Issues Without June Secure Boot Update

Microsoft says a Secure Boot certificate expiration in June will affect most Windows devices. Users must install a May 2026 update that refreshes the certificates; otherwise devices may fail to boot securely.

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Secure Boot certificates verify a device’s boot integrity. The May update adds a “SecureBoot” folder in Windows 11 to store refreshed certificates, which must be applied before the June deadline.

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The update was first released on May 12, 2026, refreshed with a release note on May 13, and a warning on May 15 that it might fail to install. Microsoft set June 1 as the final deadline for devices lacking the new certificates.

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Microsoft urges users to update certificates before the June deadline, stating that the update adds high-confidence device-targeting data to broaden automatic delivery of new Secure Boot certificates. It also notes that a missing certificate will trigger a red stop icon in the Windows Security app.

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After the update, PCs usually restart once to load the new certificates. The new “SecureBoot” folder is expected and does not need deletion. If the update fails, the system may roll back, leaving the certificate unchanged and risking a boot error.

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The notice language has been described as not the clearest, leaving users unsure of the exact steps. Some report needing multiple reboots, while others see the warning that the update might fail to install. The vague guidance has raised concerns about possible widespread disruption.

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Microsoft refers only to most Windows devices, while a Forbes note indicates that the exact number of affected PCs is unknown. The precise behavior of the rollback mechanism also remains unclear.

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• “take action to update certificates in advance.” — Microsoft

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• “reboot your PC once or twice to finish applying the changes.” — Windows Latest

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• “might affect the ability of certain personal and business devices to boot securely if not updated in time.” — Microsoft

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• “ We will not know how many PCs are affected by this for some time.” — Forbes article

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Microsoft will monitor rollout signals and will only deliver certificates after devices show successful update behavior, keeping the rollout phased. Users should check the Windows Security app for the red stop icon and ensure the update is installed before the June deadline.

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