# CVE-2026-98683: smb: client: flush dirty data before zeroing a range

> A race condition in the Linux kernel SMB client allows attackers to read stale data from zeroed file ranges due to missing dirty page flushes.

- **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:** 19 Oct 2026
- **Also known as:** BELL-CVE-2026-98683, DEBIAN-CVE-2026-98683, GHSA-f8wg-49h3-2qvh, UBUNTU-CVE-2026-98683

## What is CVE-2026-98683?

CVE-2026-98683 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: flush dirty data before zeroing a range

smb3_zero_range() emulates FALLOC_FL_ZERO_RANGE by invalidating the
page cache over the target range with truncate_pagecache_range() and
then issuing FSCTL_SET_ZERO_DATA to the server.

Dirty data was only flushed conditionally, when the range reached or
extended EOF.  For a purely interior zero range that does not reach
EOF, no flush happened, so a dirty folio overlapping the range could
be written back to the server after the FSCTL and refill the range
that was just zeroed with stale data.

Fix this by unconditionally flushing and waiting for dirty data in the
range before invalidating the page cache and issuing
FSCTL_SET_ZERO_DATA, exactly as was done for smb3_punch_hole() in
commit d7d2adcd022b ("smb/client: flush dirty data before punching a
hole"); the two paths are structurally identical here.

This is observed as generic/363 randomly reading stale data where a
zeroed range is expected against Windows Server.

## Which versions are affected by CVE-2026-98683?


## How do I fix CVE-2026-98683?

Apply the vendor's patch.

## Is CVE-2026-98683 being exploited?

There is no known exploitation of CVE-2026-98683 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-98683 and fix it if it is affected.

What it is: CVE-2026-98683 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-2026-98683 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-2026-98683/ (Markdown: https://insights.sbomify.com/CVE-2026-98683/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-98683
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-98683
- OSV: https://osv.dev/vulnerability/CVE-2026-98683

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-98683/
Summaries are generated and may contain mistakes; the official description above is the record.