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CVE-2026-53359 ("Januscape") is a use-after-free vulnerability in the Linux kernel's KVM/x86 shadow MMU implementation. The bug is in shadow paging child-page reuse: when a guest-visible PDE mapping is changed from a large 2MB mapping to a non-leaf 4KB path, KVM can incorrectly reuse an existing struct kvm_mmu_page because kvm_mmu_get_child_sp() does not validate that the page role matches the new walk. This creates a role mismatch between a page originally created with direct=1 and a path that requires direct=0. A subsequent leaf 4KB SPTE installation records an rmap entry for the resolved GFN, but when the child shadow page is later zapped, gfn computation follows the stale direct=1 semantics and fails to remove the recorded rmap entry. If the memslot is then deleted, the shadow page is freed while the stale rmap entry remains. Later kernel paths that walk that GFN, including dirty logging and MMU notifier invalidation, can dereference an sptep pointing into freed memory, resulting in a use-after-free. Public reporting states the flaw can be triggered through guest-side actions alone and affects KVM/x86 on both Intel and AMD hosts.
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17 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.
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Cross-references every affected SKU, including bundled OEM variants.
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