CVE-2026-98505 mm/damon/vaddr: avoid hw-driven pte updates during damon_hugetlb_mkold()
A race condition in the Linux kernel's DAMON virtual address module can cause loss of hardware-updated page table bits, potentially leading to data corruption.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Not stated
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-98505?
CVE-2026-98505 is a vulnerability in Linux, published on 18 Oct 2026.
Official description
In the Linux kernel, the following vulnerability has been resolved:
mm/damon/vaddr: avoid hw-driven pte updates during damon_hugetlb_mkold()
damon_hugetlb_mkold() reads the page table entry into a local variable, unsets the accessed bit in the variable, and updates the page table entry with the updated variable value. If hardware updates the same page table entry in parallel, the hw updates could be lost. For example, hardware-updated dirty bits might be lost.
Avoid the parallel updates by clearing the page table entry when reading it together, using huge_ptep_get_and_clear(). If a parallel write to the memory is made after the clearing, the hw will see the page table entry is cleared, trigger page fault and wait until it is handled. The page fault handling will wait for damon_hugetlb_mkold() due to the page table lock.
Because hugetlbfs is an in-memory file system and hugetlb pages cannot be reclaimed, no critical issue is expected to my best knowledge. But definitely this is a nasty bug that should be fixed sooner rather than later.
The issue was discovered [1] by Sashiko.
Which versions are affected by CVE-2026-98505?
How do I fix CVE-2026-98505?
Apply the vendor's patch.
Is CVE-2026-98505 being exploited?
There is no known exploitation of CVE-2026-98505 in the wild and no public exploit code.
Sources
Also known as AZL-108903, BELL-CVE-2026-98505, DEBIAN-CVE-2026-98505, GHSA-mr9h-5fpp-c352, UBUNTU-CVE-2026-98505.