CVE-2026-31456

OVERVIEW CVE-2026-31456 is a race condition vulnerability in the Linux kernel's memory management subsystem, specifically in the pagewalk functionality. The vulnerability occurs when concurrent threads attempt to split a PUD (Page Upper Directory) entry while another thread simultaneously refaults the same entry, causing the pagewalk code to attempt traversal of a PMD (Page Middle Directory) range that no longer exists. This affects all Linux kernel versions containing the vulnerable pagewalk code and can be triggered through legitimate operations such as reading numa_maps while VFIO-PCI performs DMA setup on large memory regions. SEVERITY The vulnerability has a relatively low severity profile with a FAUCET Risk Score of 20.0/100 and an EPSS score of 0.00017, indicating minimal real-world exploitation likelihood. The attack vector is local, as it requires the ability to trigger concurrent memory operations on the same system. The complexity is moderate, requiring specific timing conditions between pagewalk operations and memory refaulting. The primary impact is availability through denial of service, manifesting as a kernel BUG and system crash rather than privilege escalation or data compromise. The vulnerability does not appear in the CISA Known Exploited Vulnerabilities catalog, and no public exploit code is widely available. EXPLOITATION STATUS There is no evidence of active exploitation in the wild. The vulnerability requires precise timing between specific kernel subsystem operations and is not amenable to remote exploitation. The issue was identified through internal kernel development processes rather than external security research, and the fix has been integrated into the Linux kernel through standard patching mechanisms. Community attention remains minimal given the low severity classification and local-only attack surface.