# CVE-2026-98686: smb: client: discard post-EOF pagecache when extending a file via zero range

> A local attacker can read stale pagecache data beyond the end of a file when extending it via SMB zero range operations.

- **Severity:** Not scored
- **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:** Yes
- **Published:** 18 Oct 2026
- **Updated:** 21 Oct 2026
- **Also known as:** AZL-109121, BELL-CVE-2026-98686, DEBIAN-CVE-2026-98686, GHSA-826x-h445-jqcg, UBUNTU-CVE-2026-98686

## What is CVE-2026-98686?

CVE-2026-98686 is a vulnerability in Linux, published on 18 Oct 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:

smb: client: discard post-EOF pagecache when extending a file via zero range

smb3_zero_range() removed the pagecache only for the range being zeroed,
so when it extends the file the folio straddling the old EOF - which may
hold data dirtied past EOF through an mmap - was never dropped and became
visible as file content once the file was extended.

Lower the discard boundary to the smaller of the zero-range offset and the
old EOF.

## Which versions are affected by CVE-2026-98686?


## How do I fix CVE-2026-98686?

Apply the vendor's patch.

## Is CVE-2026-98686 being exploited?

There is no known exploitation of CVE-2026-98686 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-98686 and fix it if it is affected.

What it is: CVE-2026-98686 is a vulnerability in Linux, published on 18 Oct 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-98686 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-2026-98686/ (Markdown: https://insights.sbomify.com/CVE-2026-98686/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-98686
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-98686
- OSV: https://osv.dev/vulnerability/CVE-2026-98686

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-98686/
Summaries are generated and may contain mistakes; the official description above is the record.