CVE-2026-72173 fs/proc/task_mmu: do not warn on seeing non-migration pmd entry
A stale kernel warning in the proc filesystem can be triggered by local users, potentially causing log spam or system instability.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-72173?
CVE-2026-72173 is a denial of service vulnerability in Linux, published on 15 Aug 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
In the Linux kernel, the following vulnerability has been resolved:
fs/proc/task_mmu: do not warn on seeing non-migration pmd entry
Patch series "mm/hmm: A fix and a selftest", v3.
Patch 1 fixes a stale warning present from the time when only migration softleaf entries were supported at the PMD level.
Patch 2 adds some code into hmm-tests.c which exercises the pagemap path for PMD device-private entries.
This patch (of 2):
pagemap_pmd_range_thp() warns if a non-present PMD is not a migration entry. This became false once device-private entries at the PMD level were added.
Therefore, remove the stale migration-only assertion.
Which versions are affected by CVE-2026-72173?
How do I fix CVE-2026-72173?
Apply the vendor's patch.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-72173 being exploited?
There is no known exploitation of CVE-2026-72173 in the wild and no public exploit code.
Sources
Also known as DEBIAN-CVE-2026-72173, GHSA-hw29-pcpv-9423, UBUNTU-CVE-2026-72173.