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CVE-2026-53359
KVM: x86: Fix shadow paging use-after-free due to unexpected role
Published 2026-07-04 (4 months ago) by the Linux kernel CNA. Subsystem arch/x86. Debian urgency: not yet assigned.
What to do, per Debian release
Debian's own status for CVE-2026-53359 in every release this site tracks, and what each one means in practice. Every status below is the one the Debian Security Team publishes for this CVE. source
| Release | Status | Version | What this means |
|---|---|---|---|
| Debian 12bookworm | fixedDLA-4688-1 · 2026-07-18 · text | 6.1.177-1 | Update the kernel and reboot. DLA-4688-1 shipped the fix on 2026-07-18, in 6.1.177-1. A running kernel keeps the old code until the machine restarts. |
| Debian 13trixie | fixedDSA-6381-1 · 2026-07-05 · text | 6.12.95-1 | Update the kernel and reboot. DSA-6381-1 shipped the fix on 2026-07-05, in 6.12.95-1. A running kernel keeps the old code until the machine restarts. |
| Debian 14forky | fixed | 7.1.3-1 | Update the kernel and reboot. Fixed in 7.1.3-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.1.3-1 | Update the kernel and reboot. Fixed in 7.1.3-1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
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.
Where it lives
The fix touches these files. If the subsystem is one you do not use, the practical exposure is lower, though the package is still the vulnerable one.
arch/x86/kvm/mmu/mmu.c
- What this is
- KERNEL VIRTUAL MACHINE FOR X86 (KVM/x86)MAINTAINERS section matched on arch/x86/kvm/*/ · kvm@vger.kernel.org · Supported
Show whether Debian builds this, per release
Not established. This site could not find the build rule for the affected file in the kernel trees Debian ships, so it has no answer about whether Debian compiles this code. Read that as unknown, never as absent.
- bookworm, trixie, forky, sid?
- ?
- not established - no Makefile entry for the affected file
Where a release above reads "not established", no build rule for the affected file was found in that release's kernel tree. That is a gap in this lookup, not a finding that the code is absent.
From the configuration Debian publishes for every kernel flavour it builds. It covers only the architectures Debian ships a linux-config package for, and nothing about a kernel you built yourself. Debian's own status above stays authoritative about the source package.MAINTAINERS
Signals
- Published
- 2026-07-04 (4 months ago)source
- CVSS
- 8.8 high
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:Hsource recompute it - Attack vector
- local (AV:L)source
- EPSS
- 0.98%, higher than 61.5% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- not yet assignedsource
- Subsystem
- arch/x86
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 2.6.36 | 5.15.222 | 0b5e8ead71e6 |
| 2.6.36 | 6.1.177 | b1337aae5e19 |
| 2.6.36 | 6.6.144 | 9291654d69e0 |
| 2.6.36 | 6.12.95 | 2ad3afa40ac6 |
| 2.6.36 | 6.18.38 | 5e470998a23e |
| 2.6.36 | 7.1.3 | 1ae7d5a6db6c |
| 2.6.36 | 7.2 | 81ccda30b4e8 |
Debian advisories
| Advisory | Date | Shipped to | Debian |
|---|---|---|---|
| DLA-4700-1 | 2026-07-26 | bullseye 6.1.177-1~deb11u1 | tracker |
| DLA-4688-1 | 2026-07-18 | bookworm 6.1.177-1 | tracker |
| DSA-6381-1 | 2026-07-05 | trixie 6.12.95-1 | tracker |
Why the CNA scored it this way
Quoted from the kernel CNA's own scoring file, word for word. A highlighted metric carries the most severe value CVSS v3.1 defines for it, which is what pushes the score up. source
- AV:LAttack vector, local
- The vulnerable code is reached through local KVM guest execution/KVM ioctls and shadow-MMU page fault handling, not by network packets or adjacent/physical input. In the highest reasonable scenario, an attacker runs code in a guest on an x86 KVM host with shadow paging/nested virtualization exposed.
- AC:LAttack complexity, low
- The bug is a deterministic role-confusion/use-after-free in shadow page reuse, and the attacker can drive the guest mapping changes and later rmap walks needed to hit it. No condition outside attacker influence is required once the vulnerable KVM configuration is present.
- PR:LPrivileges required, low
- The attacker needs the ability to run code in a KVM guest or otherwise access KVM VM execution interfaces, but does not need host root or administrative privileges. This is low privilege relative to the host security boundary.
- UI:NUser interaction, none
- No victim user action is required after the attacker-controlled guest or KVM workload is running. The trigger is caused by guest execution and KVM memory-management operations.
- S:CScope, changed
- This is a KVM guest-to-host escape class vulnerability, crossing from the guest security authority into the host kernel/hypervisor. Compromise can affect resources outside the guest’s own scope.
- C:HConfidentiality impact, high
- The stale rmap entry dereferences an SPTE pointer in freed shadow-page memory, creating a kernel use-after-free. Such memory corruption can be leveraged for host kernel information disclosure and arbitrary memory access.
- I:HIntegrity impact, high
- The use-after-free can corrupt host kernel shadow-MMU/rmap state and provides a plausible path to host kernel code execution or arbitrary modification. Public analysis treats this as a KVM escape class issue, so high integrity impact is defensible.
- A:HAvailability impact, high
- At minimum, walking the stale rmap can dereference freed memory and crash or panic the host kernel. A malicious guest can repeatedly trigger the condition, causing high availability impact to the host and colocated guests.