Apple has stopped signing iOS 26.5 and iOS 26.5.1, which means iPhone users can no longer downgrade to these versions after installing a newer update. The change follows the release of iOS 26.5.2, which arrived last week with an important security fix.
Apple usually stops signing older iOS versions after a newer update has been available for some time and has not shown major problems. In this case, Apple waited about a week after releasing iOS 26.5.2 before closing the downgrade path for iOS 26.5.1.
Apple marked iOS 26.5.2 as an important security update because it fixed serious vulnerabilities affecting iPhone users. The company also moved some planned iOS 26.6 fixes forward so users could receive better protection sooner.
iOS 26.5.2 is now the latest public iPhone software version. Meanwhile, Apple is testing iOS 26.6 beta 4 with developers, while iOS 27 beta 3 is also available for testing.
