CVE-2026-72011 in Linux
Summary
by MITRE • 08/15/2026
In the Linux kernel, the following vulnerability has been resolved:
s390/diag: Add missing array_index_nospec() call to memtop_get_page_count()
'level' is user space controlled and used to read from an array. Add the missing array_index_nospec() call to prevent speculative execution.
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Analysis
by VulDB Data Team • 08/15/2026
The vulnerability identified in the Linux kernel s390 architecture relates to a potential speculative execution flaw in the diag subsystem that could allow unauthorized access to kernel memory through improper bounds checking. This issue affects systems utilizing the s390 architecture where user space applications can influence the 'level' parameter used in memory management operations. The vulnerability stems from a missing array_index_nospec() function call within the memtop_get_page_count() routine, which is responsible for handling memory topology information retrieval.
The technical flaw manifests when user space controlled data flows into kernel space through the 'level' parameter that determines array indexing operations. Without proper bounds validation using array_index_nospec(), the kernel's memory management subsystem becomes susceptible to speculative execution attacks where malicious actors could potentially infer kernel memory layout information through side-channel timing attacks. This vulnerability specifically impacts the s390 architecture's diagnostic functionality and represents a classic example of improper input validation leading to speculative execution risks.
The operational impact of this vulnerability extends beyond simple information disclosure, as it creates potential pathways for privilege escalation and memory corruption attacks within the kernel space. Attackers could exploit this flaw to gain unauthorized access to sensitive kernel data structures, potentially leading to complete system compromise. The vulnerability affects systems running Linux kernels with s390 architecture support where diagnostic operations are enabled, making it particularly concerning for mainframe environments that rely heavily on these subsystems for monitoring and management purposes.
Mitigation strategies should focus on implementing the missing array_index_nospec() call to properly validate array indices before speculative execution occurs. System administrators should ensure all affected kernel versions receive immediate updates from their distribution vendors, with particular attention to mainframe deployments where s390 architecture diagnostics are actively used. The fix aligns with security best practices for preventing speculative execution attacks and follows established guidelines for kernel memory safety. Additionally, organizations should conduct comprehensive security assessments of their kernel configurations to identify similar patterns where user-controlled inputs might flow into kernel space operations without proper bounds checking mechanisms.
This vulnerability type corresponds to CWE-129 and CWE-787 in the Common Weakness Enumeration catalog, representing improper input validation and out-of-bounds read issues. From an ATT&CK framework perspective, this vulnerability maps to techniques involving privilege escalation through kernel exploits and information gathering via side-channel attacks. The remediation approach demonstrates the importance of following secure coding practices for kernel development, particularly when handling user-controlled data that flows into kernel space operations where speculative execution can create attack vectors. Organizations should implement regular kernel security audits and ensure comprehensive testing of memory management subsystems to prevent similar vulnerabilities from emerging in other parts of the kernel codebase.