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CVE-2026-23401 is a flaw in the Linux kernel KVM x86 MMU logic for installing emulated MMIO shadow page table entries. When KVM creates an MMIO SPTE, it must first drop or zap any existing shadow-present SPTE for the same entry. The vulnerable behavior failed to do this in a specific state transition, leaving a stale shadow-present SPTE in place while installing an MMIO SPTE. The issue arises when guest memory backing a shadowed guest page table entry is modified outside KVM's normal guest-write handling, such as by host userspace changing a shadowed guest PTE from a memslot-backed mapping to emulated MMIO. If the guest then triggers the relevant page fault, KVM can install the MMIO SPTE without first invalidating the existing present SPTE. This results in inconsistent shadow MMU state and can trigger warnings in the KVM MMU path, including the MMIO SPTE marking logic.
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No public exploit code observed for this vulnerability.
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25 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.
A Linux kernel KVM vulnerability that can lead to privilege escalation or denial of service due to improper shadow page table entry handling.
A Linux kernel KVM vulnerability that can lead to privilege escalation or denial of service due to improper shadow page table entry handling.
A Linux kernel KVM vulnerability that can lead to privilege escalation or denial of service due to improper shadow page table entry handling.
A Linux kernel KVM vulnerability that can lead to privilege escalation or denial of service due to improper shadow page table entry handling.
Query your assets running an affected version, and investigate the blast radius.
Every observed campaign linking this CVE to a named adversary.
Malware families riding this exploit, with evidence and IOCs.
YARA, Sigma, Snort, and vendor rules, auto-deployed to your SIEM.
Cross-references every affected SKU, including bundled OEM variants.
Community discussion across Reddit, Mastodon, and other social sources.