{"id":"AZL-109349","summary":"CVE-2026-98717 affecting package kernel 6.6.157.1-1","details":"In the Linux kernel, the following vulnerability has been resolved:\n\nKVM: x86/mmu: Bail from shadow walks if the root is invalid or a dummy\n\nWhen walking shadow page tables, immediately terminate the walk if the root\nis a \"dummy\" root, i.e. a root whose top-level page table is backed by the\nzero page, but otherwise doesn't exist.  If memslot creation races with a\nstage-2 page fault (EPT violation or #NPF) from L2, then if the stars align,\nKVM will attempt to walk shadow page tables using the zero page and hit a\nNULL pointer deref.\n\n  BUG: kernel NULL pointer dereference, address: 0000000000000021\n  #PF: supervisor read access in kernel mode\n  #PF: error_code(0x0000) - not-present page\n  PGD 0 P4D 0\n  Oops: Oops: 0000 [#1] SMP\n  CPU: 30 UID: 1000 PID: 941 Comm: qemu Not tainted 7.2.0-rc2-1b731e5ded48-next-vm #1741 PREEMPTLAZY\n  Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/2015\n  RIP: 0010:__kvm_mmu_invalidate_addr+0xea/0x210 [kvm]\n  Call Trace:\n   \u003cTASK\u003e\n   kvm_mmu_invalidate_addr+0x92/0xe0 [kvm]\n   __kvm_inject_emulated_page_fault+0x67/0x80 [kvm]\n   ept_page_fault+0x160/0x850 [kvm]\n   kvm_mmu_do_page_fault+0x102/0x1f0 [kvm]\n   kvm_mmu_page_fault+0x8e/0x6b0 [kvm]\n   vmx_handle_exit+0x163/0x640 [kvm_intel]\n   kvm_arch_vcpu_ioctl_run+0x960/0x2120 [kvm]\n   kvm_vcpu_ioctl+0x2c7/0x970 [kvm]\n   __x64_sys_ioctl+0x90/0xd0\n   do_syscall_64+0x67/0x5f0\n   entry_SYSCALL_64_after_hwframe+0x4b/0x53\n  RIP: 0033:0x7f606d0b53bb\n\nOpportunistically harden the shadow walks against fully invalid roots, but\nWARN, as all callers are expected/required to pre-check for a valid root.\nDon't WARN in the dummy root case as the whole point of using a dummy root\nis to provide a root that's valid enough to enter the guest, i.e. it should\nJust Work for all flows except those that *need* to know about dummy roots.\n\nAlternatively, KVM could allocate a dedicated page and associated shadow\npage structure for the dummy root, which is very tempting as it such an\napproach should be more resilient against unexpected behavior.  But that\nwould be a much larger and thus riskier change than simply terminating\nwalks of dummy roots.","modified":"2026-10-19T14:17:05.889500802Z","published":"2026-10-18T16:17:25Z","upstream":["CVE-2026-98717"],"references":[{"type":"WEB","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-98717"}],"affected":[{"package":{"name":"kernel","ecosystem":"Azure Linux:3","purl":"pkg:rpm/azure-linux/kernel"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"last_affected":"6.6.157.1-1"}]}],"database_specific":{"source":"https://github.com/microsoft/AzureLinuxVulnerabilityData/blob/main/osv/AZL-109349.json"}}],"schema_version":"1.9.0"}