CVE-2026-53359
HighCVSS 8.8Exploitation Probability (EPSS)
Low risk2th percentile - higher than 2% of all known CVEs
Summary
A use-after-free vulnerability was found in the Linux kernel's KVM shadow paging for x86. The bug occurs due to a role mismatch when a PDE mapping is changed from outside the guest, causing reuse of a kvm_mmu_page with an incorrect role. This leads to a dangling rmap entry after memslot deletion, and subsequent operations on the freed page cause memory corruption.
Risk Assessment
The organization faces potential system crashes, data leaks, or privilege escalation in KVM virtualized environments. A malicious guest can intentionally trigger this vulnerability, leading to uncontrolled kernel behavior.
Recommendation
Immediately update the Linux kernel to a version containing the fix (commit 0cb2af2ea66ad and related). If updating is not possible, restrict access to memslot management and PDE modifications from the guest.
Original NVD description (English source)
In the Linux kernel, the following vulnerability has been resolved: KVM: x86: Fix shadow paging use-after-free due to unexpected role Commit 0cb2af2ea66ad ("KVM: x86: Fix shadow paging use-after-free due to unexpected GFN") fixed a shadow paging mismatch between stored and computed GFNs; the bug could be triggered by changing a PDE mapping from outside the guest, and then deleting a memslot. The rmap_remove() call would miss entries created after the PDE change because the GFN of the leaf SPTE does not match the GFN of the struct kvm_mmu_page. A similar hole however remains if the modified PDE points to a non-leaf page. In this case the gfn can be made to match, but the role does not match: the original large 2MB page creates a kvm_mmu_page with direct=1, while the new 4KB needs a kvm_mmu_page with direct=0. However, kvm_mmu_get_child_sp() does not compare the role, and therefore reuses the page. The next step is installing a leaf (4KB) SPTE on the new path which records an rmap entry under the gfn resolved by the walk. But when that child is zapped its parent kvm_mmu_page has direct=1 and kvm_mmu_page_get_gfn() computes the gfn for the 4KB page as sp->gfn + index instead of using sp->shadowed_translation[] (or sp->gfns[] in older kernels). It therefore fails to remove the recorded entry. When the memslot is dropped the shadow page is freed but the rmap entry survives, as in the scenario that was already fixed. Code that later walks that gfn (dirty logging, MMU notifier invalidation, and so on) dereferences an sptep that lies in the freed page, causing the use-after-free.