The Linux kernel originally emitted a stale warning when the proc/task_mmu module encountered a non‑present PMD that was not a migration entry. With the addition of device‑private PMD entries, the condition that only allowed migration entries became incorrect, producing a false warning. This bug does not allow attackers to compromise confidentiality, integrity, or availability; it merely generates misleading diagnostic output.

The affected product is the Linux kernel. Kernels that have the older proc/task_mmu logic, before inclusion of the mm/hmm: A fix and a selftest patch series v3, are potentially impacted. No specific version range is provided, so all releases prior to the patch may exhibit the stale warning.

Because the warning is purely informational and unrelated to any security boundary, the risk remains low. The CVSS score is 5.5, the EPSS score is < 1%, and it is not listed in the CISA KEV catalog. There is no known attack vector or exploitation path, so the bug does not pose a security threat.