CVE-2023-5090

What it actually does

Improper check in svm_set_x2apic_msr_interception() allows a guest to directly access host x2APIC MSRs upon APIC reset, bypassing intended interception and enabling denial of service.

Why it matters to the business

Virtualized workloads on affected Linux kernels may experience unexpected host-level crashes or instability, increasing downtime risk for systems relying on KVM virtualization.

How an attack unfolds

An attacker with local access to a guest VM triggers an APIC reset to exploit the missing MSR interception check, gaining direct access to host x2APIC registers and inducing a denial of service condition on the host.

How to fix it

Apply upstream Linux kernel patches addressing the improper check in svm_set_x2apic_msr_interception(); monitor Red Hat and kernel mailing lists for backported fixes in affected enterprise distributions since no fixed versions are currently listed.

How to confirm the fix worked

Verify kernel source contains the corrected svm_set_x2apic_msr_interception() logic, confirm updated kernel packages are installed across hosts, and test guest APIC reset behavior under controlled conditions.

Typical attack path

1. Obtain local access inside a KVM guest VM
2. Trigger APIC reset from guest context
3. Bypass MSR interception to reach host registers
4. Induce host denial of service via MSR manipulation

How to detect it

Review kernel logs and hypervisor audit trails for unexpected APIC reset events or anomalous MSR access attempts originating from guest contexts.

What your security team should do

• Prioritize kernel updates on all KVM hosts once patches become available
• Restrict untrusted guest workloads on affected kernels until remediation
• Review virtualization configurations to minimize guest-to-host attack surface