VulnerabilityPublished 18 Oct 2026Updated 21 Oct 2026

CVE-2026-98717: Linux kernel · KVM: x86/mmu: Bail from shadow walks if the root is invalid or a dummy

Affects Linux kernelSource CVE Database V5

Not known to be exploited · fixed in e1bcabc07efd029ab414894127411129ffdb8b48 : update Linux kernel when convenient.

Data as of 26 Oct 2026, 16:00 UTC

Severity

Unrated

Rated by Threat Radar · CVSS not yet scored by NVD

EPSS: 0.2% chance of exploitation in 30 days – higher than 9% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in e1bcabc07efd029ab414894127411129ffdb8b48, b6249c1d5665098c8bf12f8d3e4712bf04c775bc, 951fce1510645ba5df38da6fb85ece5726ec347d +2

Exploitation evidence

Disclosed: evidence found.
CVE published 18 Oct 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Upgrade to a fixed release listed under Affected software.

Affected software

Product	Affected	Fixed in
LinuxLinux	Affected ≥ 0e3223d8d00ac05849661f1b8b476d3caca251cf, < e1bcabc07efd029ab414894127411129ffdb8b48	Fixed in e1bcabc07efd029ab414894127411129ffdb8b48
LinuxLinux	Affected ≥ 0e3223d8d00ac05849661f1b8b476d3caca251cf, < b6249c1d5665098c8bf12f8d3e4712bf04c775bc	Fixed in b6249c1d5665098c8bf12f8d3e4712bf04c775bc
LinuxLinux	Affected ≥ 0e3223d8d00ac05849661f1b8b476d3caca251cf, < 951fce1510645ba5df38da6fb85ece5726ec347d	Fixed in 951fce1510645ba5df38da6fb85ece5726ec347d
LinuxLinux	Affected ≥ 0e3223d8d00ac05849661f1b8b476d3caca251cf, < 681e31f03ec9219099a66a0f6e1bc48e1b5aa914	Fixed in 681e31f03ec9219099a66a0f6e1bc48e1b5aa914
LinuxLinux	Affected ≥ 0e3223d8d00ac05849661f1b8b476d3caca251cf, < 97c1dcce17ef27853860c781f9912257e6adbf7c	Fixed in 97c1dcce17ef27853860c781f9912257e6adbf7c
LinuxLinux	Affected =6.6	Fixed in–

Description

In the Linux kernel, the following vulnerability has been resolved: KVM: x86/mmu: Bail from shadow walks if the root is invalid or a dummy When walking shadow page tables, immediately terminate the walk if the root is a "dummy" root, i.e. a root whose top-level page table is backed by the zero page, but otherwise doesn't exist. If memslot creation races with a stage-2 page fault (EPT violation or #NPF) from L2, then if the stars align, KVM will attempt to walk shadow page tables using the zero page and hit a NULL pointer deref. BUG: kernel NULL pointer dereference, address: 0000000000000021 #PF: supervisor read access in kernel mode #PF: error_code(0x0000) - not-present page PGD 0 P4D 0 Oops: Oops: 0000 [#1] SMP CPU: 30 UID: 1000 PID: 941 Comm: qemu Not tainted 7.2.0-rc2-1b731e5ded48-next-vm #1741 PREEMPTLAZY Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/2015 RIP: 0010:__kvm_mmu_invalidate_addr+0xea/0x210 [kvm] Call Trace: <TASK> kvm_mmu_invalidate_addr+0x92/0xe0 [kvm] __kvm_inject_emulated_page_fault+0x67/0x80 [kvm] ept_page_fault+0x160/0x850 [kvm] kvm_mmu_do_page_fault+0x102/0x1f0 [kvm] kvm_mmu_page_fault+0x8e/0x6b0 [kvm] vmx_handle_exit+0x163/0x640 [kvm_intel] kvm_arch_vcpu_ioctl_run+0x960/0x2120 [kvm] kvm_vcpu_ioctl+0x2c7/0x970 [kvm] __x64_sys_ioctl+0x90/0xd0 do_syscall_64+0x67/0x5f0 entry_SYSCALL_64_after_hwframe+0x4b/0x53 RIP: 0033:0x7f606d0b53bb Opportunistically harden the shadow walks against fully invalid roots, but WARN, as all callers are expected/required to pre-check for a valid root. Don't WARN in the dummy root case as the whole point of using a dummy root is to provide a root that's valid enough to enter the guest, i.e. it should Just Work for all flows except those that *need* to know about dummy roots. Alternatively, KVM could allocate a dedicated page and associated shadow page structure for the dummy root, which is very tempting as it such an approach should be more resilient against unexpected behavior. But that would be a much larger and thus riskier change than simply terminating walks of dummy roots.

References

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