Описание
In the Linux kernel, the following vulnerability has been resolved:
KVM: x86: Check for invalid/obsolete root after making MMU pages available
Check for a "stale" page fault, i.e. for an invalid and/or obsolete root,
after making MMU pages available for the shadow MMU. If reclaiming shadow
pages zaps an in-use root, i.e. marks it invalid, then KVM will attempt to
map memory into an invalid root. On its own, populating an invalid root is
"fine", but because child shadow pages inherit their parent's role, any
children created during the map/fetch will be created as invalid pages,
thus violating KVM's invariant that invalid pages are never on the list of
active MMU pages.
Note, the underlying flaw has existed since KVM first started tracking
invalid roots in 2008 (commit 2e53d63acba7, "KVM: MMU: ignore zapped root
pagetables"), but the true badness only came along in 2020 (Linux 5.9)
with the invariant that invalid shadow pages can't be on the list of
active pages.
Note #2, inheriting role.invalid when creating child shadow pages is also
far from ideal; that flaw will be addressed separately.
A flaw was found in KVM in the Linux kernel. This vulnerability occurs due to improper validation of memory management unit (MMU) page roots after these pages are made available. An attacker could exploit this by triggering a scenario where KVM attempts to map memory into an invalid root, causing child shadow pages to inherit an invalid state. This violates KVM's internal integrity rules, potentially leading to system instability or a denial of service within the virtualized environment.
Отчет
Red Hat rates the security impact of this issue as moderate. A flaw was found in the KVM x86 memory management unit (MMU) handling in the Linux kernel, affecting the kernel and kernel-rt packages in Red Hat Enterprise Linux and the kernels in Red Hat In-Vehicle OS. KVM checked for an invalid or obsolete root before making MMU pages available for the shadow MMU, so if reclaiming shadow pages zapped an in-use root and marked it invalid, a subsequent "stale" page fault caused KVM to map memory into that invalid root. Child shadow pages created during the mapping inherited their parent's invalid role, violating KVM's invariant that invalid pages are never on the list of active MMU pages. A local attacker with low privileges could exploit this race condition to trigger system instability or a denial of service within the virtualized environment. Exploitation requires winning a race in the MMU reclaim path, which Red Hat reflects as high attack complexity in its CVSS 3.1 score of 7.0; the upstream CVE record scores the issue 8.8 with low attack complexity and changed scope. Red Hat Enterprise Linux 6 and 7 Extended Life Cycle Support kernels are not affected because the vulnerable code is not present in those versions. Fixes for the affected products are being pursued and delivered through updates.
Меры по смягчению последствий
Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability.
Затронутые пакеты
| Платформа | Пакет | Состояние | Рекомендация | Релиз |
|---|---|---|---|---|
| Red Hat Enterprise Linux 6 | kernel | Not affected | ||
| Red Hat Enterprise Linux 7 | kernel | Not affected | ||
| Red Hat Enterprise Linux 7 | kernel-rt | Not affected | ||
| Red Hat Enterprise Linux 9 | kernel-rt | Affected | ||
| Red Hat Enterprise Linux 10 | kernel | Fixed | RHSA-2026:45114 | 24.07.2026 |
| Red Hat Enterprise Linux 10.0 Extended Update Support | kernel | Fixed | RHSA-2026:49030 | 31.07.2026 |
| Red Hat Enterprise Linux 8 | kernel-rt | Fixed | RHSA-2026:45116 | 24.07.2026 |
| Red Hat Enterprise Linux 8 | kernel | Fixed | RHSA-2026:45115 | 24.07.2026 |
| Red Hat Enterprise Linux 8.8 Telecommunications Update Service | kernel | Fixed | RHSA-2026:47869 | 29.07.2026 |
| Red Hat Enterprise Linux 8.8 Update Services for SAP Solutions | kernel | Fixed | RHSA-2026:47869 | 29.07.2026 |
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Дополнительная информация
Статус:
7 High
CVSS3
Связанные уязвимости
In the Linux kernel, the following vulnerability has been resolved: KVM: x86: Check for invalid/obsolete root *after* making MMU pages available Check for a "stale" page fault, i.e. for an invalid and/or obsolete root, after making MMU pages available for the shadow MMU. If reclaiming shadow pages zaps an in-use root, i.e. marks it invalid, then KVM will attempt to map memory into an invalid root. On its own, populating an invalid root is "fine", but because child shadow pages inherit their parent's role, any children created during the map/fetch will be created as invalid pages, thus violating KVM's invariant that invalid pages are never on the list of active MMU pages. Note, the underlying flaw has existed since KVM first started tracking invalid roots in 2008 (commit 2e53d63acba7, "KVM: MMU: ignore zapped root pagetables"), but the true badness only came along in 2020 (Linux 5.9) with the invariant that invalid shadow pages can't be on the list of active pages. Note #2, inherit...
In the Linux kernel, the following vulnerability has been resolved: KVM: x86: Check for invalid/obsolete root *after* making MMU pages available Check for a "stale" page fault, i.e. for an invalid and/or obsolete root, after making MMU pages available for the shadow MMU. If reclaiming shadow pages zaps an in-use root, i.e. marks it invalid, then KVM will attempt to map memory into an invalid root. On its own, populating an invalid root is "fine", but because child shadow pages inherit their parent's role, any children created during the map/fetch will be created as invalid pages, thus violating KVM's invariant that invalid pages are never on the list of active MMU pages. Note, the underlying flaw has existed since KVM first started tracking invalid roots in 2008 (commit 2e53d63acba7, "KVM: MMU: ignore zapped root pagetables"), but the true badness only came along in 2020 (Linux 5.9) with the invariant that invalid shadow pages can't be on the list of active pages. Note #2, inheri
KVM: x86: Check for invalid/obsolete root *after* making MMU pages available
In the Linux kernel, the following vulnerability has been resolved: K ...
In the Linux kernel, the following vulnerability has been resolved: KVM: x86: Check for invalid/obsolete root *after* making MMU pages available Check for a "stale" page fault, i.e. for an invalid and/or obsolete root, after making MMU pages available for the shadow MMU. If reclaiming shadow pages zaps an in-use root, i.e. marks it invalid, then KVM will attempt to map memory into an invalid root. On its own, populating an invalid root is "fine", but because child shadow pages inherit their parent's role, any children created during the map/fetch will be created as invalid pages, thus violating KVM's invariant that invalid pages are never on the list of active MMU pages. Note, the underlying flaw has existed since KVM first started tracking invalid roots in 2008 (commit 2e53d63acba7, "KVM: MMU: ignore zapped root pagetables"), but the true badness only came along in 2020 (Linux 5.9) with the invariant that invalid shadow pages can't be on the list of active pages. Note #2, inh...
7 High
CVSS3