# 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.

- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Not stated
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 18 Oct 2026
- **Updated:** 21 Oct 2026
- **Also known as:** AZL-108903, BELL-CVE-2026-98505, DEBIAN-CVE-2026-98505, GHSA-mr9h-5fpp-c352, UBUNTU-CVE-2026-98505

## 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.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-98505 and fix it if it is affected.

What it is: CVE-2026-98505 is a vulnerability in Linux, published on 18 Oct 2026. 
Exploitation: There is no known exploitation of CVE-2026-98505 in the wild and no public exploit code.

Affected product: Linux. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-98505/ (Markdown: https://insights.sbomify.com/CVE-2026-98505/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-98505
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-98505
- OSV: https://osv.dev/vulnerability/CVE-2026-98505

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-98505/
Summaries are generated and may contain mistakes; the official description above is the record.