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Microsoft confirms April Windows updates cause backup failures - BleepingComputer

Introduction to the Issue

Microsoft has recently confirmed that the April 2026 security updates are causing failures in third-party backup applications. This issue specifically affects applications that utilize the psmounterex.sys driver, which is a crucial component for many backup solutions. As a result, users may experience difficulties in creating backups, which can potentially lead to data loss in the event of a system failure or other catastrophic events.

Cause of the Problem

The root cause of the problem lies in the changes introduced by the April 2026 security updates. These updates, intended to enhance the security posture of Windows systems, inadvertently interfere with the operation of the psmounterex.sys driver. This driver is used by various third-party backup applications to mount and manage backup volumes. Due to the updates, these applications are now experiencing failures, rendering them unable to perform their intended functions.

Impact and Concerns

The impact of this issue is significant, as it affects the ability of users to create reliable backups. In the event of a system failure or data corruption, backups are often the only means of retrieving critical data. With backup applications failing due to the April 2026 updates, users are exposed to a higher risk of data loss. This situation is particularly concerning for businesses and organizations that rely heavily on data integrity and availability. Microsoft's confirmation of the issue is the first step towards resolving the problem, but users are advised to exercise caution and explore alternative backup strategies until a fix is made available.

Conclusion and Future Steps

In conclusion, the confirmation by Microsoft of the backup failures caused by the April 2026 Windows updates is a critical step in addressing the issue. Users of affected third-party backup applications are advised to monitor the situation closely and consider interim measures to ensure their data is protected. Microsoft is expected to release updates or patches to resolve the compatibility issues with the psmounterex.sys driver, restoring the functionality of backup applications. As the situation develops, it is essential for users to remain vigilant and adhere to best practices for data backup and recovery to mitigate potential risks.