CVE-2017-1000252

What it actually does

A guest VM can supply an out-of-bounds guest_irq value that triggers an assertion failure inside the host KVM subsystem (arch/x86/kvm/vmx.c and virt/kvm/eventfd.c), causing the hypervisor to hang or crash.

Why it matters to the business

A compromised or malicious guest can take down the entire hypervisor, resulting in denial of service for all other virtual machines on the host and unplanned outages for workloads that depend on them.

How an attack unfolds

An attacker with code execution inside a guest crafts a request that passes an illegal guest_irq value to the KVM eventfd path; the host kernel performs no bounds check, hits an assertion, and the hypervisor process terminates or deadlocks, stopping every VM on the physical server.

How to fix it

Upgrade the Linux kernel to a version containing commit 36ae3c0a36b7456432fedce38ae2f7bd3e01a563 or later; apply the vendor-supplied kernel package that includes this fix and reboot the host.

How to confirm the fix worked

Verify the running kernel contains commit 36ae3c0a36b7456432fedce38ae2f7bd3e01a563 or a back-port that removes the unchecked guest_irq path; confirm the assertion no longer triggers under synthetic out-of-bounds IRQ tests.

Typical attack path

1. Obtain code execution or control of a guest virtual machine
2. Trigger the KVM eventfd path with an out-of-bounds guest_irq value from guest context
3. Cause assertion failure in the host kernel leading to hypervisor hang or crash
4. All co-located VMs lose service until the host is restarted

How to detect it

Review host kernel logs for assertion failures or oops messages originating from kvm/vmx.c or eventfd.c around the time of guest activity; correlate with guest-initiated device or IRQ operations preceding the crash.

What your security team should do

• Patch all affected hosts to a fixed kernel within the next maintenance window
• Prioritize hosts running untrusted or multi-tenant workloads
• Monitor for hypervisor crashes and guest-initiated IRQ anomalies until patching is complete
• Review guest isolation policies to reduce the blast radius of any future KVM issues