An issue exists in includes/specials/SpecialMovePage.php in MediaWiki prior to 1.39.7, 1.40.x prior to 1.40.3, and 1.41.x prior to 1.41.1. If a user with the necessary rights to move the page opens Special:MovePage for a page with tens of thousands of subpages, then the page will exceed the maximum request time, leading to a denial of service.
Vulmon