Microsoft Confirms Backup Issues Caused by April Updates

Microsoft has confirmed that the April 2026 security updates are leading to failures in third-party backup applications. These issues are attributed to the psmounterex.sys driver, which was modified in the updates. Users are reporting difficulties in creating and restoring backups, potentially leading to data loss. The problems have been reported by several users in online forums and social media. Affected applications include a variety of backup solutions that rely on the psmounterex.sys driver.

Microsoft has already initiated an investigation to determine the exact causes of the errors. In an official statement, Microsoft explained that the issues do not occur with its own backup solutions such as Windows Backup or OneDrive. The security updates were originally released to address several critical security vulnerabilities documented in CVE-2026-1234. These vulnerabilities affect a range of Windows versions, including Windows 10 and Windows 11. Microsoft recommends installing the updates to protect systems from potential attacks.

Nonetheless, the issues with backup applications are considered serious, as many businesses rely on these solutions. To minimize the impact, Microsoft advises users to perform a full backup of their data before installing the updates. The company is working on a patch to resolve the issues with the psmounterex.sys driver; however, a timeline for the release of this patch has not yet been provided. The community has already begun discussing alternative backup methods to mitigate risks during the resolution process.

Some users have found temporary solutions by reverting to older versions of the backup software. However, Microsoft has warned that this is not recommended, as older software versions may also have security vulnerabilities. The situation is also impacting the IT departments of many companies, which are now forced to rethink their backup strategies. Experts recommend regularly updating backup software and checking compatibility with the latest Windows updates.

The uncertainty regarding the stability of backup solutions could lead to an increase in demand for professional IT services. Microsoft has announced that further information about the issues and planned solutions will be released in the coming days. Users are encouraged to follow Microsoft's official channels for the latest updates. According to the BSI, the security vulnerability CVE-2026-1234 affects approximately 50,000 systems in Germany.