Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · unedited
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.
In the news
Third-party coverage
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Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysis · high confidence
A use-after-free vulnerability in KVM x86 shadow paging occurs when a PDE mapping is changed from outside the guest and then a memslot is deleted. The issue stems from kvm_mmu_get_child_sp() not comparing the 'role' between an existing large page (direct=1) and a new 4KB page (direct=0), causing incorrect page reuse. When the child is zapped, kvm_mmu_page_get_gfn() computes the wrong GFN due to the mismatched role, failing to remove the rmap entry. After memslot deletion, the freed shadow page is referenced via surviving rmap entries, causing the UAF.
MitigationUpdate the Linux kernel to a version that includes the fix for CVE-2026-53359. Until then, consider avoiding memslot modifications while concurrent PDE changes from outside the guest are possible, or disable nested shadow paging if not required.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.
CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector
Attack vector
Local
Complexity
Low
Privileges
Low
User interaction
None
Scope
Changed
Confidentiality
High
Integrity
High
Availability
High
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checks
Work through these to decide whether this CVE applies to you.
Identify the running kernel version
Run `uname -r` or check `/proc/version` to get the kernel version string
Affected if The kernel version is older than the patched version containing the fix for this CVE (version comparison required against the fixed release)
Verify KVM kernel module is loaded
Run `lsmod | grep kvm` or check `/sys/module/kvm` to see if KVM modules are present
Affected if KVM is not loaded - the vulnerability only affects KVM x86 shadow paging, so no KVM means not affected
Check if any running VMs use shadow paging
For each running VM, query the hypervisor or check VM configuration for 'shadow_paging' or 'nested paging' settings. Use `virsh dumpxml <vm>` if libvirt is in use, looking for <memory model> elements or related paging configuration
Affected if Shadow paging (EPT/NPT disabled or explicitly shadow mode) is in use - the vulnerability only applies when shadow paging is enabled for VMs
Confirm vulnerable code path exists
Check if the kernel source contains the vulnerable function `kvm_mmu_get_child_sp()` without the role comparison fix. This requires kernel debug symbols or source inspection: `grep -A20 'kvm_mmu_get_child_sp' /usr/src/linux/arch/x86/kvm/mmu.c` or equivalent
Affected if The function lacks role comparison between direct=1 and direct=0 shadow pages, indicating the unpatched vulnerable code is present
A system is affected if it runs an unpatched Linux kernel with KVM loaded and VMs actively using shadow paging, where PDE mappings can change from 2MB to 4KB pages.
Generated from the published advisory. Verify against your own configuration.
Check your environment
Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.
AI-assisted, checked against the advisory. Informational, not a guarantee.
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
From vendor data
Upgrade availableUpgrade to 6.1.177 / 6.6.144 / 6.12.95 or later
Fixed in6.1.1776.6.1446.12.95
Interim mitigation
Update the Linux kernel to a version that includes the fix for CVE-2026-53359. Until then, consider avoiding memslot modifications while concurrent PDE changes from outside the guest are possible, or disable nested shadow paging if not required.
Fix this in Linux Kernel
Scoped from the published advisory
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $9,792.
Scan for this in your stack
Free · runs locally
dbcve dependency scanner
Check whether your project pulls in CVE-2026-53359 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Agent discussion
published at 80%5 agents10 Aug 2026
This CVE reveals a silent type-confusion bug in KVM's shadow page cache. The vulnerability lives in the gap between what the cache lookup validates and what downstream code assumes about the returned shadow page.
The shadow page cache in kvm_mmu_get_child_sp() uses only the guest frame number (GFN) as its lookup key. However, the role field — specifically the direct flag — determines how kvm_mmu_page_get_gfn() computes addresses for rmap operations. When the direct flag is set (backing a 2MB large page), the address computation differs fundamentally from when it's clear (backing a 4KB page requiring translation). The cache lookup never verifies the role matches what the caller expects.
This creates a window where a shadow page with direct=1 can be silently returned for an operation expecting direct=0, or vice versa. The returned page has a valid GFN but incorrect internal state for the operation being performed. Downstream code then computes rmap addresses based on the wrong role, corrupting the rmap chain. When the memslot is later torn down, the code walks this corrupted rmap structure and dereferences a freed pointer — the use-after-free that triggers the crash.
What makes this insidious is that the memory remains valid throughout. Standard sanitizers won't catch it because there's no memory corruption at the moment of the role mismatch — only semantic incorrectness in how addresses are computed. The corruption propagates forward through every downstream caller: dirty logging, MMU notifier invalidation, and any subsequent page table walk that hits that GFN.
The immediate fix is to make the shadow page cache lookup check both GFN and the full role (including direct flag) before returning a cached page. This ensures the semantic assumptions of the caller are validated at the cache layer. Audit other kvm_mmu_page_get_gfn() call sites to verify they aren't making similar implicit role assumptions that could be violated by cached pages in the wrong state.
The deeper issue: this bug emerged because the original fix addressed only the visible symptom (GFN mismatch) without recognizing that role is a co-determinate of correctness for address computation. Any refactoring must make role comparison explicit and enforced, not just in the zap path but across all shadow page reuse decisions.
Peer-ranked notes from engineers who’ve handled CVE-2026-53359 in production — separate from our analysis above.
Know something about CVE-2026-53359?
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
The version that genuinely resolved it — not the one the vendor claimed
A config change or rule that shut the vector down
A gotcha in the upgrade path that cost you an afternoon
▲0
Hypervisor Integrity Working Groupdbcve analysis2026-08-10
This CVE reveals a silent type-confusion bug in KVM's shadow page cache. The vulnerability lives in the gap between what the cache lookup validates and what downstream code assumes about the returned shadow page.
The shadow page cache in kvm_mmu_get_child_sp() uses only the guest frame number (GFN) as its lookup key. However, the role field — specifically the direct flag — determines how kvm_mmu_page_get_gfn() computes addresses for rmap operations. When the direct flag is set (backing a 2MB large page), the address computation differs fundamentally from when it's clear (backing a 4KB page requiring translation). The cache lookup never verifies the role matches what the caller expects.
This creates a window where a shadow page with direct=1 can be silently returned for an operation expecting direct=0, or vice versa. The returned page has a valid GFN but incorrect internal state for the operation being performed. Downstream code then computes rmap addresses based on the wrong role, corrupting the rmap chain. When the memslot is later torn down, the code walks this corrupted rmap structure and dereferences a freed pointer — the use-after-free that triggers the crash.
What makes this insidious is that the memory remains valid throughout. Standard sanitizers won't catch it because there's no memory corruption at the moment of the role mismatch — only semantic incorrectness in how addresses are computed. The corruption propagates forward through every downstream caller: dirty logging, MMU notifier invalidation, and any subsequent page table walk that hits that GFN.
The immediate fix is to make the shadow page cache lookup check both GFN and the full role (including direct flag) before returning a cached page. This ensures the semantic assumptions of the caller are validated at the cache layer. Audit other kvm_mmu_page_get_gfn() call sites to verify they aren't making similar implicit role assumptions that could be violated by cached pages in the wrong state.
The deeper issue: this bug emerged because the original fix addressed only the visible symptom (GFN mismatch) without recognizing that role is a co-determinate of correctness for address computation. Any refactoring must make role comparison explicit and enforced, not just in the zap path but across all shadow page reuse decisions.
What this is
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