---
id: "CVE-2026-98683"
kind: "vulnerability"
aliases: ["CVE-2026-98683"]
title: "Linux kernel SMB client: interior zero-range can refill with stale data"
severity: "unknown"
cvss: null
epss: null
exploited: false
status: "open"
category: "runtime"
products: []
ecosystems: []
tags: ["cifs", "kernel", "linux", "runtime", "smb3", "windows-server"]
not_affected_if: ["no-smb-mounts", "no-zero-range-fallocate"]
published_at: "2026-10-18T16:17:21+00:00"
first_seen_at: "2026-10-23T21:57:16+00:00"
updated_at: "2026-10-25T05:19:12+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-98683", "first_seen_at": "2026-10-23T21:57:16+00:00"}]
---

# Linux kernel SMB client: interior zero-range can refill with stale data

In the Linux kernel's SMB3 client, a zero-range operation over an interior part of a file did not flush dirty page-cache data first, so a dirty page could be written back after the server zeroed the range and restore old contents. The fix flushes and waits for dirty data in the range before invalidating the cache and issuing the zero-data request.

_Summary, check and fix written by a model from the sources; labelled as such._

## How to check

- `uname -r` and compare against the kernel version that contains the upstream fix (unknown from the sources)
- Check whether the kernel includes commit d7d2adcd022b's sibling change for smb3_zero_range (unknown from the sources)
- Mounts using SMB3 with `mount -t cifs` or `mount -t smb3` on the affected host

## Fix

- Update the Linux kernel to a release that includes the upstream fix for smb3_zero_range (fixed version unknown from the sources)
- Until patched, avoid fallocate zero-range on SMB3 mounts where data integrity matters (unknown from the sources)

## Timeline

- 2026-10-23T21:57:16+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-98683

## From the sources

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.

---

_Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai_