CVE-2024-50139 is a vulnerability identified in the Linux kernel specifically affecting the Kernel-based Virtual Machine (KVM) implementation on the ARM64 architecture. The issue is a shift-out-of-bounds bug detected by the Undefined Behavior Sanitizer (UBSAN) when running virtual machines (VMs) on a host kernel with Memory Tagging Extension (MTE) enabled. The vulnerability arises from an improper shift operation in the source file arch/arm64/kvm/sys_regs.c at line 1988, where a shift exponent of 33 is applied to a 32-bit integer type, which is invalid and leads to undefined behavior. This bug manifests during the reset of system registers for a virtual CPU (vCPU) within KVM, as indicated by the call trace involving functions such as kvm_reset_sys_regs and kvm_reset_vcpu. The flaw could potentially cause kernel crashes or unpredictable behavior in the KVM subsystem on ARM64 hosts, particularly when MTE is enabled. Although no known exploits are reported in the wild, the vulnerability affects the stability and reliability of virtualization environments on ARM64 Linux systems, which are increasingly used in cloud and edge computing scenarios. The issue has been addressed in Linux kernel version 6.12.0-rc2 and later, but the patch links are not provided in the source information. This vulnerability does not have an assigned CVSS score yet, and it requires privileged access (root) to trigger, as it involves KVM and qemu-kvm processes. No user interaction is needed once the attacker has sufficient privileges to run or manage VMs on the affected host.

For European organizations, the impact of CVE-2024-50139 primarily concerns entities relying on ARM64-based Linux virtualization infrastructures, such as cloud service providers, telecom operators deploying edge computing, and enterprises using ARM64 servers for virtualization. The vulnerability could lead to denial of service (DoS) conditions by causing kernel panics or crashes in KVM virtual machines, disrupting critical services and workloads. In environments where ARM64 virtualization is used for multi-tenant cloud hosting, this could affect service availability and reliability, potentially leading to operational downtime and financial losses. Although there is no evidence of privilege escalation or remote code execution, the instability introduced by this bug could be exploited by malicious insiders or attackers with administrative access to degrade system performance or availability. Given the growing adoption of ARM64 architectures in Europe, especially in sectors like telecommunications (5G infrastructure), automotive, and cloud computing, the vulnerability poses a tangible risk to the continuity of services relying on these platforms.

To mitigate CVE-2024-50139, European organizations should: 1) Apply the latest Linux kernel updates that include the fix for this vulnerability, specifically versions 6.12.0-rc2 or later, as soon as they become available and tested in their environments. 2) For environments using KVM on ARM64 hosts with MTE enabled, temporarily consider disabling MTE if kernel updates cannot be immediately applied, as MTE triggers the bug. 3) Restrict administrative access to KVM and virtualization management interfaces to trusted personnel only, minimizing the risk of exploitation by insiders. 4) Implement robust monitoring of kernel logs and virtualization subsystem behavior to detect anomalies or crashes related to this issue. 5) In cloud or multi-tenant environments, isolate ARM64 virtualization hosts and apply strict access controls to prevent unauthorized VM creation or manipulation. 6) Coordinate with hardware and software vendors to ensure compatibility and timely patch deployment, especially for ARM64 server platforms widely used in European data centers.