# CVE-2026-98843: netfs: zero gaps in read-gaps folio to avoid writing back stale data

> An attacker with local access could read stale data from the Linux kernel netfs subsystem due to improper zeroing of read gaps.

- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 18 Oct 2026
- **Updated:** 19 Oct 2026
- **Also known as:** BELL-CVE-2026-98843, DEBIAN-CVE-2026-98843, GHSA-3x6r-43qp-fxh7, UBUNTU-CVE-2026-98843

## What is CVE-2026-98843?

CVE-2026-98843 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:

netfs: zero gaps in read-gaps folio to avoid writing back stale data

netfs_read_gaps() leaves gaps around a streaming write's dirty region
unread on the server side, so a short/EOF response there left stale
folio content that later got written back.

Zero it after the read completes, not before: netfs_wait_for_read()
returns rreq->transferred once ret >= 0, so build an iterator over the
same bvec array the read used, advance past ret, and zero the rest.
The dirty region already maps to sink pages in that array rather than
the real folio, so this can't touch it, and only the actual shortfall
gets zeroed instead of the whole gap upfront.

## Which versions are affected by CVE-2026-98843?


## How do I fix CVE-2026-98843?

Apply the vendor's patch.

## Is CVE-2026-98843 being exploited?

There is no known exploitation of CVE-2026-98843 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-98843 and fix it if it is affected.

What it is: CVE-2026-98843 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-2026-98843 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-2026-98843/ (Markdown: https://insights.sbomify.com/CVE-2026-98843/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-98843
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-98843
- OSV: https://osv.dev/vulnerability/CVE-2026-98843

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-98843/
Summaries are generated and may contain mistakes; the official description above is the record.