# CVE-2026-72217: SUNRPC: Bound-check xdr_buf_to_bvec() stores before writing

> An out-of-bounds write in the Linux kernel SUNRPC module allows attackers to corrupt memory, potentially leading to code execution or privilege escalation.

- **Severity:** Critical 9.8 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H`)
- **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-2026-72217, DEBIAN-CVE-2026-72217, GHSA-jffc-255g-3gq9, UBUNTU-CVE-2026-72217

## What is CVE-2026-72217?

CVE-2026-72217 is a critical memory corruption 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:

SUNRPC: Bound-check xdr_buf_to_bvec() stores before writing

xdr_buf_to_bvec() writes a bio_vec into the caller's array before
testing whether that slot is in range, and the head branch performs
the store with no check at all. When the caller's budget is exactly
used up, the next store lands one element past the end of the array.
The overflow label returns count - 1, which masks the surplus store
but cannot undo it.

rq_bvec, the array passed by nfsd_vfs_write(), is allocated to
exactly rq_maxpages entries with no slack. The OOB store can land in
adjacent slab memory; the bv_len and bv_offset fields written there
are derived from client-supplied RPC payload sizes.

Move the in-range check ahead of the store in the head, page-loop,
and tail branches. With the check at the top of each sequence, count
is incremented only after a successful store, so the overflow label
can return count directly.

## Which versions are affected by CVE-2026-72217?


## How do I fix CVE-2026-72217?

Apply the vendor's patch.

## Is CVE-2026-72217 being exploited?

There is no known exploitation of CVE-2026-72217 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-72217 and fix it if it is affected.

What it is: CVE-2026-72217 is a critical memory corruption 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-2026-72217 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-2026-72217/ (Markdown: https://insights.sbomify.com/CVE-2026-72217/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-72217
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-72217
- OSV: https://osv.dev/vulnerability/CVE-2026-72217

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-72217/
Summaries are generated and may contain mistakes; the official description above is the record.