CVE-2025-23141 is a vulnerability identified in the Linux kernel's KVM (Kernel-based Virtual Machine) subsystem, specifically affecting the x86 architecture virtualization implementation. The issue arises from improper synchronization when userspace requests the multiprocessor (MP) state of a virtual CPU (vCPU) via the KVM_GET_MP_STATE ioctl. In certain edge cases, particularly when a vCPU is running a nested virtualization scenario (L2 guest) with a pending INIT signal and a TRIPLE_FAULT request, the kernel fails to properly acquire the SRCU (Sleepable Read-Copy Update) lock protecting guest memory accesses. This can lead to a nested VM-Exit event triggered during the retrieval of the MP state, which in turn causes the kernel to access guest memory without proper synchronization. The vulnerability was initially discovered through fuzzing with syzkaller on an internal Google kernel and reproduced upstream by manipulating the triple_fault_event_test selftest to simulate the problematic conditions. The kernel's lockdep debugging output indicates suspicious RCU usage and a stack trace involving KVM functions such as kvm_vcpu_ioctl, kvm_check_nested_events, and kvm_apic_accept_events. This flaw could potentially lead to race conditions or memory corruption within the KVM module when handling nested virtualization events, possibly causing system instability or crashes. Although no direct exploit in the wild is known, the vulnerability affects Linux kernel versions containing the specified commit hashes and requires a scenario involving nested virtualization with specific vCPU states and ioctl calls. The lack of a CVSS score suggests this is a newly disclosed issue requiring careful assessment and patching by Linux kernel maintainers and users running KVM with nested virtualization enabled.

For European organizations, the impact of CVE-2025-23141 is primarily relevant to environments utilizing Linux-based virtualization infrastructure, especially those leveraging nested virtualization capabilities for cloud services, testing, or development. Organizations running KVM on servers or cloud platforms that host nested virtual machines could experience system instability, crashes, or potential denial of service if this vulnerability is exploited or triggered unintentionally. While there is no evidence of remote code execution or privilege escalation directly from this flaw, the risk of memory corruption or race conditions in the hypervisor layer could undermine the reliability and security of virtualized workloads. This is particularly critical for data centers, cloud service providers, and enterprises relying on Linux virtualization for multi-tenant environments or sensitive workloads. Disruptions caused by this vulnerability could affect service availability and data integrity, impacting business continuity and compliance with European data protection regulations. Additionally, the complexity of nested virtualization scenarios means that only specialized setups are at risk, but these are common in advanced cloud and research infrastructures prevalent in Europe.

To mitigate CVE-2025-23141, European organizations should: 1) Apply the latest Linux kernel updates and patches that address this vulnerability as soon as they become available from trusted sources such as the Linux kernel mailing list or vendor distributions. 2) Review and restrict the use of nested virtualization features in KVM environments, disabling nested virtualization where it is not strictly necessary to reduce the attack surface. 3) Implement strict access controls on userspace interfaces that can invoke KVM ioctls, ensuring only trusted and authorized users or processes can interact with the virtualization subsystem. 4) Monitor kernel logs and virtualization subsystem behavior for anomalies or crashes related to VM-Exit handling or MP state retrieval, enabling early detection of exploitation attempts or instability. 5) Conduct thorough testing of virtualization workloads after patching to confirm stability and absence of regressions, especially in nested VM scenarios. 6) Engage with Linux distribution security advisories and virtualization vendors for coordinated updates and guidance tailored to specific deployment environments. These steps go beyond generic advice by focusing on controlling nested virtualization usage and securing the ioctl interface, which are critical vectors for this vulnerability.