Winsage
May 18, 2026
Microsoft has acknowledged a significant issue with the May 2026 Windows 11 security update, KB5089549, where users are encountering difficulties in installation, specifically the 0x800f0922 error code. This issue is primarily due to insufficient free space on the EFI System Partition (ESP), especially for devices with 10 MB or less available. The installation may fail during the reboot phase at around 35–36% completion, with users receiving notifications like "Something didn't go as planned. Undoing changes." Log entries may indicate insufficient ESP free space, such as "SpaceCheck: Insufficient free space" and "ServicingBootFiles failed. Error = 0x70." Microsoft recommends affected users utilize the Known Issue Rollback feature to reverse problematic updates and advises IT departments to install and configure the relevant Group Policy to address the issue.