CVE-2025-37958: 
Linux Kernel vulnerability analysis and mitigation

CVE-2025-37958 is a vulnerability discovered in the Linux kernel's memory management subsystem, specifically in the huge memory handling code. The vulnerability was disclosed on May 20, 2025, affecting the mm/huge_memory component. When migrating a Transparent Huge Page (THP), concurrent access to the PMD migration entry during a deferred split scan can lead to an invalid address access (NVD, RedHat).

The vulnerability occurs in the splithugepmdlocked function where concurrent access to the PMD migration entry during a deferred split scan leads to an invalid address access. The issue stems from improper handling of PMD migration entries, where there is no need to use pmdtoswpentry and pfnswapentrytopage to verify the equality of the target folio. The vulnerability has been assigned a CVSS v3.1 score of 7.0 (AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H) (RedHat).

The vulnerability can result in invalid address access and potential system crashes. The bug was initially found by syzkaller on an internal kernel and later confirmed on upstream systems. The impact is demonstrated through a page fault error for address ffffea60001db008, which could lead to system instability (NVD).

The vulnerability has been resolved in the Linux kernel through a fix that implements proper checking of the PMD migration entry and returns early when necessary. Red Hat has marked this as 'Fix deferred' for Red Hat Enterprise Linux 9 and 10, while versions 6, 7, and 8 are either not affected or out of support scope (RedHat).