---
id: CVE-2026-89641
title: 'cifs: clear tcon after cifsFileInfo_put() in cifs_file_set_size()'
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  cifs: clear tcon after cifsFileInfo_put() in cifs_file_set_size()

  When the else branch of cifs_file_set_size() finds a writable file handle
  via find_writable_file(), i…
severity: high
cvss: 7.8
cvssVector: 'CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H'
cvssSource: cna
cwe:
  - CWE-825
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= 110fee6b9bb58a5c50047fc2594d415f741b591e <
    4f18c9e7ee464aaae5cd9fccdb943b3fcb4655d4
  - >-
    Linux >= 110fee6b9bb58a5c50047fc2594d415f741b591e <
    4bea15d9c7683218f57b8c1f5f0aa75cab76af8d
  - >-
    Linux >= 110fee6b9bb58a5c50047fc2594d415f741b591e <
    b96db32fed8dfb2478d7c208f89bf383beed1535
  - Linux 6.18
published: '2026-09-11'
updated: '2026-10-19'
sourceUpdated: '2026-10-19T08:50:13.143Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-89641'
references:
  - url: 'https://git.kernel.org/stable/c/4f18c9e7ee464aaae5cd9fccdb943b3fcb4655d4'
  - url: 'https://git.kernel.org/stable/c/4bea15d9c7683218f57b8c1f5f0aa75cab76af8d'
  - url: 'https://git.kernel.org/stable/c/b96db32fed8dfb2478d7c208f89bf383beed1535'
  - url: >-
      https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-89641.json
  - url: 'https://access.redhat.com/security/cve/CVE-2026-89641'
  - url: 'https://bugzilla.redhat.com/show_bug.cgi?id=2532505'
  - url: 'https://www.cve.org/CVERecord?id=CVE-2026-89641'
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2026-89641'
  - url: >-
      https://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2026/CVE-2026-89641.mbox
tags:
  - cve.org
  - csaf
  - vex
  - red-hat
epss: 0.0014
epssPercentile: 0.03293
scores:
  cna: 7.8
  vendor: 7
ingestedAt: '2026-09-14T15:23:07.473Z'
---

## Overview

In the Linux kernel, the following vulnerability has been resolved:

cifs: clear tcon after cifsFileInfo_put() in cifs_file_set_size()

When the else branch of cifs_file_set_size() finds a writable file handle
via find_writable_file(), it borrows tcon and server from the handle's
tlink, attempts the handle-based set_file_size() RPC, and then releases
the handle with cifsFileInfo_put().

If set_file_size() fails, execution falls through to the path-based
fallback, which reuses the borrowed tcon and server under the
"if (tcon == NULL)" guard.  Since tcon is not NULL at that point, the
guard is skipped.  If cifsFileInfo_put() dropped the last reference on a
tlink that was already removed from the tlink tree (TCON_LINK_IN_TREE
cleared, as happens during reconnection or session teardown),
cifs_put_tlink() will have freed tcon; the subsequent set_path_size()
call is then a use-after-free.

Setting tcon = NULL after cifsFileInfo_put() causes the existing guard
to take the cifs_sb_tlink() path, which acquires a fresh reference for
the path-based operation or fails cleanly if the session is gone.

## Affected

- `Linux >= 110fee6b9bb58a5c50047fc2594d415f741b591e < 4f18c9e7ee464aaae5cd9fccdb943b3fcb4655d4`
- `Linux >= 110fee6b9bb58a5c50047fc2594d415f741b591e < 4bea15d9c7683218f57b8c1f5f0aa75cab76af8d`
- `Linux >= 110fee6b9bb58a5c50047fc2594d415f741b591e < b96db32fed8dfb2478d7c208f89bf383beed1535`
- `Linux 6.18`

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.

## Vendor advisories

- **Red Hat VEX** · Moderate · affected: Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 9, Red Hat OpenShift Container Platform 4 · no fix planned: Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 9, Red Hat OpenShift Container Platform 4 · updated 2026-09-15 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-89641.json)