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CVE-2026-40402 is a use-after-free vulnerability in Windows Hyper-V, Microsoft's built-in hypervisor. The flaw can be triggered by an attacker operating from within a guest virtual machine and is described as allowing the host kernel to read from a memory address chosen by the attacker, creating conditions for guest-to-host escalation. The vulnerability affects the isolation boundary enforced by Hyper-V and can permit elevation of privilege from a guest context into the host environment. In addition to direct privilege escalation risk, the flaw can destabilize the host during exploitation attempts.
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What it means. What to do now. Patch path, mitigations, and the assume-compromise checklist.
What an attacker gets, and what they’ve been doing with it.
If you can’t patch tonight, do this now.
Patch, then assume compromise.
No public exploits tracked yet. Mallory keeps watching.
No public exploit code observed for this vulnerability.
Products and vendors Mallory has correlated with this vulnerability. Open in Mallory to drill down to specific CPE configurations and version ranges.
Vendor-confirmed product mapping. Mallory continuously reconciles this list against your asset inventory.
5 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.
A use-after-free vulnerability in Windows Hyper-V that allows unauthorized attackers to gain SYSTEM privileges and access the Hyper-V host environment.
A use-after-free vulnerability in Windows Hyper-V that allows guest-to-host escape, affecting the hypervisor and potentially other tenants.
A Windows Hyper-V privilege escalation vulnerability with particular significance in multi-tenant and private cloud environments due to potential guest-to-host escape impact.
An elevation of privilege vulnerability in Hyper-V that may enable guest-to-host escalation by causing the host kernel to read from an attacker-chosen memory address.
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.