Copyright © 2012 Red Hat, Inc. All rights reserved. Important 2026-07-04T00:00:00 kernel: KVM: x86: Fix shadow paging use-after-free due to unexpected role 7.8 CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:H CWE-825

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.

A flaw was found in the Linux kernel's Kernel-based Virtual Machine (KVM) x86 shadow paging mechanism. This vulnerability occurs when a host page directory entry (PDE) mapping is changed from within the guest, leading to an unexpected role mismatch in shadow paging. This mismatch can cause a use-after-free condition, where the system attempts to access memory that has already been released. Such a condition can lead to system instability, denial of service, potentially the execution of arbitrary code or guest-to-host escape.

This is an Important flaw in the KVM x86 shadow paging mechanism where an attacker with privileged access inside the guest VM could trigger a use-after-free condition by manipulating page directory entries on the host. This could lead to system instability, denial of service, or potentially arbitrary code execution on the host. In Red Hat Enterprise Linux 7, nested virtualization for KVM is a Technology Preview feature and the nested parameter defaults to 0 (disabled) for both kvm_intel and kvm_amd. This vulnerability can be mitigated by disabling nested virtualization. Create a file in `/etc/modprobe.d/` with a descriptive name, such as `cve-2026-53359-mitigation.conf`. In that file, disable nested virtualization for the `kvm_intel` and `kvm_amd` kernel modules: ``` options kvm-intel nested=0 options kvm-amd nested=0 ``` Use `lsmod` to determine if either module is already loaded. If so, remove loaded modules with `modprobe -r`. To validate that nested virtualization is disabled, read the files `/sys/module/kvm_intel/parameters/nested` and `/sys/module/kvm_amd/parameters/nested`. If these modules are loaded, those files should read `N` to indicate that the feature is disabled. In OpenShift 4, a MachineConfig can be utilized to create a modprobe configuration allowing control of the module on applicable nodes. See the following article for an example. https://access.redhat.com/solutions/6979679 Red Hat Enterprise Linux 10 2026-07-09T00:00:00Z RHSA-2026:36956 kernel-0:6.12.0-211.32.1.el10_2 Red Hat Enterprise Linux 10 2026-07-22T00:00:00Z RHSA-2026:43826 kpatch-patch Red Hat Enterprise Linux 10.0 Extended Update Support 2026-07-14T00:00:00Z RHSA-2026:39371 kernel-0:6.12.0-55.88.1.el10_0 Red Hat Enterprise Linux 8 2026-07-14T00:00:00Z RHSA-2026:39082 kernel-rt-0:4.18.0-553.143.1.rt7.484.el8_10 Red Hat Enterprise Linux 8 2026-07-14T00:00:00Z RHSA-2026:39083 kernel-0:4.18.0-553.143.1.el8_10 Red Hat Enterprise Linux 8 2026-07-23T00:00:00Z RHSA-2026:44004 kpatch-patch Red Hat Enterprise Linux 8.8 Telecommunications Update Service 2026-07-17T00:00:00Z RHSA-2026:41229 kernel-0:4.18.0-477.154.1.el8_8 Red Hat Enterprise Linux 8.8 Update Services for SAP Solutions 2026-07-17T00:00:00Z RHSA-2026:41229 kernel-0:4.18.0-477.154.1.el8_8 Red Hat Enterprise Linux 8.8 Update Services for SAP Solutions 2026-07-22T00:00:00Z RHSA-2026:43847 kpatch-patch Red Hat Enterprise Linux 9 2026-07-09T00:00:00Z RHSA-2026:36957 kernel-0:5.14.0-687.24.1.el9_8 Red Hat Enterprise Linux 9 2026-07-09T00:00:00Z RHSA-2026:36957 kernel-0:5.14.0-687.24.1.el9_8 Red Hat Enterprise Linux 9 2026-07-22T00:00:00Z RHSA-2026:43825 kpatch-patch Red Hat Enterprise Linux 9.2 Update Services for SAP Solutions 2026-07-15T00:00:00Z RHSA-2026:40082 kernel-0:5.14.0-284.181.1.el9_2 Red Hat Enterprise Linux 9.2 Update Services for SAP Solutions 2026-07-15T00:00:00Z RHSA-2026:39983 kernel-rt-0:5.14.0-284.181.1.rt14.466.el9_2 Red Hat Enterprise Linux 9.2 Update Services for SAP Solutions 2026-07-23T00:00:00Z RHSA-2026:44003 kpatch-patch Red Hat Enterprise Linux 9.4 Update Services for SAP Solutions 2026-07-10T00:00:00Z RHSA-2026:37729 kernel-0:5.14.0-427.137.1.el9_4 Red Hat Enterprise Linux 9.4 Update Services for SAP Solutions 2026-07-23T00:00:00Z RHSA-2026:44006 kpatch-patch Red Hat Enterprise Linux 9.6 Extended Update Support 2026-07-13T00:00:00Z RHSA-2026:38902 kernel-0:5.14.0-570.127.1.el9_6 Red Hat Enterprise Linux 9.6 Extended Update Support 2026-07-23T00:00:00Z RHSA-2026:44007 kpatch-patch Red Hat OpenShift Container Platform 4.18 2026-07-29T00:00:00Z RHSA-2026:44230 rhcos-418.94.202607211754-0 Red Hat OpenShift Container Platform 4.19 2026-07-29T00:00:00Z RHSA-2026:44231 rhcos-4.19.9.6.202607220857-0 Red Hat OpenShift Container Platform 4.20 2026-07-21T00:00:00Z RHSA-2026:40787 rhcos-4.20.9.6.202607151937-0 Red Hat OpenShift Container Platform 4.21 2026-07-21T00:00:00Z RHSA-2026:40779 rhcos-4.21.9.6.202607151836-0 Red Hat OpenShift Container Platform 4.22 2026-07-21T00:00:00Z RHSA-2026:40764 rhcos-4.22.9.8.202607152026-0 Red Hat Enterprise Linux 6 Not affected kernel Red Hat Enterprise Linux 7 Out of support scope kernel Red Hat Enterprise Linux 7 Out of support scope kernel-rt Red Hat Enterprise Linux 9 Affected kernel-rt Red Hat Enterprise Linux for NVIDIA 26 Not affected kernel https://www.cve.org/CVERecord?id=CVE-2026-53359 https://nvd.nist.gov/vuln/detail/CVE-2026-53359 https://lore.kernel.org/linux-cve-announce/2026070403-CVE-2026-53359-4f57@gregkh/T https://www.openwall.com/lists/oss-security/2026/07/06/7 True