CVE-2025-21977 addresses a hang issue in the Linux kernel's kdump kernel when running on Hyper-V Generation 2 virtual machines. The problem arises because the hyperv_fb driver moves the framebuffer to a different memory address after conflicting with other framebuffer drivers, but the kdump kernel does not update to this new address. This causes the efifb driver to access an invalid framebuffer address, leading the Hyper-V host to throttle the VM, resulting in a hang or severe slowdown. The fix reorders framebuffer allocation steps to avoid address conflicts and ensures the kdump kernel uses the correct framebuffer address.