CVE-2025-8860 Qemu-kvm: uefi-vars: information disclosure vulnerability in uefi_vars_write callback

A flaw was found in QEMU in the uefi-vars virtual device. When the guest writes to register UEFIVARSREGBUFFERSIZE, the .write callback uefivarswrite is invoked. The function allocates a heap buffer without zeroing the memory, leaving the buffer filled with residual data from prior allocations. Wh...