CVE-2023-5090 is a vulnerability identified in the Kernel-based Virtual Machine (KVM) component of Red Hat Enterprise Linux 8. The flaw arises from an improper check in the function svm_set_x2apic_msr_interception(), which is responsible for managing Model-Specific Registers (MSRs) related to the x2APIC (Advanced Programmable Interrupt Controller) during virtual machine operations. Specifically, when a guest virtual machine resets its APIC, the improper validation allows the guest to gain direct access to host x2apic MSRs. This unauthorized access can disrupt the host's interrupt controller state, potentially causing a denial of service (DoS) condition by destabilizing the host system or causing it to crash. The vulnerability requires that the attacker has high-level privileges within the guest VM (PR:H), meaning local authenticated access with elevated rights is necessary. The attack vector is local (AV:L), and no user interaction is required (UI:N). The scope is changed (S:C), indicating that the impact extends beyond the vulnerable component to affect other components, specifically the host system. The vulnerability does not affect confidentiality or integrity but impacts availability (A:H). There are no known exploits in the wild at the time of publication, and no patches have been linked yet, but Red Hat is the vendor responsible for addressing this issue. This vulnerability is significant in environments where Red Hat Enterprise Linux 8 is used as a host for KVM virtual machines, especially in multi-tenant or cloud environments where guest VMs may be controlled by different users.

For European organizations, the primary impact of CVE-2023-5090 is the potential for denial of service on critical virtualization hosts running Red Hat Enterprise Linux 8 with KVM. This can lead to downtime of multiple virtual machines, disrupting business operations, especially in sectors relying heavily on virtualization such as finance, telecommunications, government, and cloud service providers. The vulnerability could be exploited by a malicious insider or compromised guest VM with elevated privileges to destabilize the host, causing service interruptions and potential cascading failures in virtualized environments. While confidentiality and integrity are not directly impacted, the availability loss can affect service level agreements (SLAs), compliance with regulations requiring high availability, and operational continuity. Organizations using Red Hat Enterprise Linux 8 in production environments with KVM should consider this a medium-severity risk that could escalate if combined with other vulnerabilities or misconfigurations.

To mitigate CVE-2023-5090, organizations should: 1) Monitor Red Hat advisories closely and apply patches or updates as soon as they are released to fix the improper check in svm_set_x2apic_msr_interception(). 2) Restrict and audit privileged access within guest VMs to minimize the risk of an attacker gaining the necessary high privileges to exploit this vulnerability. 3) Implement strict isolation policies between guest VMs and the host to limit the impact of any guest VM compromise. 4) Use security-enhanced virtualization configurations, such as SELinux or AppArmor profiles, to enforce access controls on KVM components. 5) Monitor logs and system behavior for unusual APIC reset activities or unexpected VM crashes that could indicate exploitation attempts. 6) Consider deploying intrusion detection systems (IDS) tailored for virtualization environments to detect anomalous guest behavior. 7) Review and harden virtualization host configurations to reduce the attack surface, including disabling unnecessary features or interfaces that could be leveraged by attackers.