# CVE-2026-72132: NFS: Charge unstable writes by request size, not folio size

> A Linux kernel NFS accounting bug allows remote attackers to cause system-wide denial of service by inflating writeback metrics via split requests.

- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 15 Aug 2026
- **Updated:** 17 Aug 2026
- **Also known as:** BELL-CVE-2026-72132, DEBIAN-CVE-2026-72132, GHSA-hmp9-jxmh-jfh2, UBUNTU-CVE-2026-72132

## What is CVE-2026-72132?

CVE-2026-72132 is a denial of service vulnerability in Linux, published on 15 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

In the Linux kernel, the following vulnerability has been resolved:

NFS: Charge unstable writes by request size, not folio size

nfs_folio_mark_unstable() and nfs_folio_clear_commit() charge and
uncharge NR_WRITEBACK/WB_WRITEBACK by folio_nr_pages(folio) once per
*request* added to or removed from a commit list. This is correct only
when a folio has a single associated request. When pg_test splits a
folio into N sub-folio requests (e.g. pNFS flexfiles striping with a
stripe unit smaller than the folio size, or plain wsize-limited
splitting), each of the N requests independently charges the whole
folio's page count, inflating the accounting by a factor of N per
folio. With large folios and small stripe units this reaches multiple
orders of magnitude: a 2 MiB folio split into 512 4 KiB requests can
charge up to 512x its real size, pushing global dirty+writeback
accounting past the system's dirty threshold and forcing every
buffered writer on the host into the hard-throttle path, including
unrelated in-kernel NFS server threads sharing the box.

Charge each request only for the pages it actually covers.

## Which versions are affected by CVE-2026-72132?


## How do I fix CVE-2026-72132?

Apply the vendor's patch.

## Is CVE-2026-72132 being exploited?

There is no known exploitation of CVE-2026-72132 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-72132 and fix it if it is affected.

What it is: CVE-2026-72132 is a denial of service vulnerability in Linux, published on 15 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-72132 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-2026-72132/ (Markdown: https://insights.sbomify.com/CVE-2026-72132/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-72132
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-72132
- OSV: https://osv.dev/vulnerability/CVE-2026-72132

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-72132/
Summaries are generated and may contain mistakes; the official description above is the record.