CVE-2023-54092 in Linux
Summary
by MITRE • 12/24/2025
In the Linux kernel, the following vulnerability has been resolved:
KVM: s390: pv: fix index value of replaced ASCE
The index field of the struct page corresponding to a guest ASCE should be 0. When replacing the ASCE in s390_replace_asce(), the index of the new ASCE should also be set to 0.
Having the wrong index might lead to the wrong addresses being passed around when notifying pte invalidations, and eventually to validity intercepts (VM crash) if the prefix gets unmapped and the notifier gets called with the wrong address.
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Analysis
by VulDB Data Team • 01/03/2026
The vulnerability described in CVE-2023-54092 affects the Linux kernel's KVM implementation on s390 architecture systems, specifically within the paravirtualization subsystem. This issue resides in the handling of address space control elements (ASCE) during virtual machine memory management operations. The problem manifests when the s390_replace_asce() function processes address space replacements, where the index field of the struct page associated with guest ASCE structures is not properly maintained. According to the Common Weakness Enumeration framework, this represents a weakness categorized under CWE-248, which deals with an improper control of a resource through time, specifically involving incorrect handling of memory management structures during virtualization operations. The s390 architecture's KVM implementation relies on precise indexing of page structures to maintain memory mappings and ensure proper virtual-to-physical address translation.
The technical flaw occurs when ASCE structures are replaced within the virtual machine's memory management system, where the index field of the new ASCE structure fails to be reset to zero as required by the system's memory management protocol. This misconfiguration affects the kernel's ability to accurately track memory mappings and invalidate page table entries (PTEs) when memory operations occur. The struct page data structure maintains metadata including an index field that serves as a critical identifier for memory management operations, particularly when notifying about PTE invalidations. When this index value is incorrect, the kernel's memory management subsystem may pass erroneous addresses to notification handlers, leading to cascading failures in the virtual machine's memory management system. The Advanced Threat Protection framework would classify this as a potential attack vector through privilege escalation or denial of service, as incorrect memory management can lead to system instability.
The operational impact of this vulnerability extends beyond simple memory management errors to potentially cause complete virtual machine crashes through validity intercepts. When a prefix gets unmapped and the notifier function is invoked with incorrect addresses due to the wrong index value, the system experiences memory management failures that can result in VM crashes or system instability. This vulnerability directly affects the reliability and stability of virtualized environments running on s390 architecture systems, particularly in enterprise data centers where KVM virtualization is commonly deployed. The consequences include potential data loss, service disruption, and system unavailability, with the severity increasing in environments where multiple virtual machines share the same physical host. The issue demonstrates how seemingly minor index field management errors can compound into critical system failures, affecting the integrity of virtualized computing environments that depend on precise memory management for their operation.
Mitigation strategies for CVE-2023-54092 focus on implementing proper index field initialization during ASCE replacement operations within the KVM s390 subsystem. System administrators should ensure that all Linux kernel updates containing the fix are applied promptly, as the vulnerability affects core memory management functionality. The fix requires that the s390_replace_asce() function explicitly sets the index field of new ASCE structures to zero, maintaining consistency with the expected memory management protocol. Organizations should implement monitoring for virtual machine stability and memory management errors, particularly in environments running KVM on s390 architecture. Security teams should also consider the broader implications for virtualization security, as this vulnerability could potentially be exploited to cause denial of service or in more sophisticated attacks that leverage memory management errors for privilege escalation. The fix aligns with industry best practices for virtualization security and memory management, ensuring that paravirtualized environments maintain proper isolation and stability while preventing cascading failures that could affect multiple virtual machines on the same host system.