Security update for xen

Open Source Vulnerabilities SUSE-SU-2026:0012-1

This update for xen fixes the following issues: Security issues fixed: - CVE-2025-27466: NULL pointer dereference in the Viridian interface when updating the reference TSC area (bsc#1248807). - CVE-2025-58142: NULL pointer dereference in the Viridian interface due to assumption that the SIM page is mapped when a synthetic timer message has to be delivered (bsc#1248807). - CVE-2025-58143: information leak and reference counter underflow in the Viridian interface due to race in the mapping of the reference TSC page (bsc#1248807). - CVE-2025-58147: incorrect input sanitisation in Viridian hypercalls using the HV_VP_SET Sparse format can lead to out-of-bounds write through `vpmask_set()` (bsc#1251271). - CVE-2025-58148: incorrect input sanitisation in Viridian hypercalls using any input format can lead to out-of-bounds read through `send_ipi()` (bsc#1251271). - CVE-2025-58149: incorrect removal of permissions on PCI device unplug allows PV guests to access memory of devices no longer assigned to them (bsc#1252692). Other issues fixed: - Several upstream bug fixes (bsc#1027519). - Failure to restart xenstored (bsc#1254180).