The Linux kernel function hugetlb_pmd_shared() incorrectly used the PMD page count to determine whether a huge‑page table was shared. As a result, shared PMD tables were never detected, causing inaccurate reference counting, misreporting of memory usage by utilities such as smaps, and a noticeable performance regression due to excessive inter‑processor interrupt broadcasts during fork+exit. The patch replaces the page count logic with a dedicated shared‑count, restoring correct detection of shared PMD tables and eliminating the accounting errors and performance issue.

The defect appears in Linux kernel releases 6.13 (including rc6 and rc7) and all 6.19 release candidates from rc1 through rc6, affecting all architectures that implement the hugetlb subsystem. Kernel packages shipped with these versions from any distribution that rely on the upstream kernel must be updated or have the patch series applied.

The CVSS score of 5.5 indicates moderate severity, while the EPSS score of less than 1 % indicates a very low probability of exploitation. The vulnerability is not listed in the CISA KEV catalog. No explicit exploitation vector is documented; the bug primarily causes incorrect memory accounting and a performance regression. The risk is therefore limited to potential denial of service through resource mismanagement rather than privilege escalation or remote code execution.