---
id: CVE-2026-97556
title: |-
  In the Linux kernel, the following vulnerability has been resolved:

  smb: client: avoid leaking refcount when cifs_sb_tlink() fails

  cifs_oplock_break() takes over the reference that
  cifs_queue_oplock_break() acquired when it queued the …
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  smb: client: avoid leaking refcount when cifs_sb_tlink() fails

  cifs_oplock_break() takes over the reference that
  cifs_queue_oplock_break() acquired when it queued the …
severity: medium
cvss: 5.5
cvssVector: 'CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H'
cwe:
  - CWE-911
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= 5ee28bcfbaacf289eb25c662a2862542ea6ce6a7 <
    55c5f095d4df14271b238f826e1392fda7b6e60e
  - >-
    Linux >= e8f5f849ffce24490eb9449e98312b66c0dba76f <
    e9c5bcc88b8337157e480c85a6d2f326bc265012
  - >-
    Linux >= e8f5f849ffce24490eb9449e98312b66c0dba76f <
    9ec991e148368e3207e98134c509a625097f7693
  - >-
    Linux >= e8f5f849ffce24490eb9449e98312b66c0dba76f <
    dd03fd658ea59821505e0e643b6b7cbdf51c4e1d
  - >-
    Linux >= e8f5f849ffce24490eb9449e98312b66c0dba76f <
    1d1b0f1d812a4011a57bc6c70492c34a2e46c6dd
  - >-
    Linux >= e8f5f849ffce24490eb9449e98312b66c0dba76f <
    23b26f4408ac3f35a482d2e5cf6fc865d4201b71
  - Linux b99f490ea87ebcca3a429fd8837067feb56a4c7c
  - Linux 6b67a6d2e50634fe127e656147c81915955e9f5e
  - Linux >= 6.1.47 < 6.1.189
  - Linux >= 5.15.128 < 5.16
  - Linux >= 6.4.12 < 6.5
  - Linux 6.5
published: '2026-09-25'
updated: '2026-10-03'
sourceUpdated: '2026-10-03T11:18:03.327'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-97556'
references:
  - url: 'https://git.kernel.org/stable/c/1d1b0f1d812a4011a57bc6c70492c34a2e46c6dd'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/23b26f4408ac3f35a482d2e5cf6fc865d4201b71'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/55c5f095d4df14271b238f826e1392fda7b6e60e'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/9ec991e148368e3207e98134c509a625097f7693'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/dd03fd658ea59821505e0e643b6b7cbdf51c4e1d'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/e9c5bcc88b8337157e480c85a6d2f326bc265012'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: >-
      https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-97556.json
  - url: 'https://access.redhat.com/security/cve/CVE-2026-97556'
  - url: 'https://bugzilla.redhat.com/show_bug.cgi?id=2541159'
  - url: 'https://www.cve.org/CVERecord?id=CVE-2026-97556'
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2026-97556'
  - url: >-
      https://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2026/CVE-2026-97556.mbox
tags:
  - nvd
  - cve.org
  - csaf
  - vex
  - red-hat
epss: 0.00211
epssPercentile: 0.11321
cvssSource: vendor
ingestedAt: '2026-09-25T11:06:38.916Z'
---

## Overview

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

smb: client: avoid leaking refcount when cifs_sb_tlink() fails

cifs_oplock_break() takes over the reference that
cifs_queue_oplock_break() acquired when it queued the work, and drops it
with _cifsFileInfo_put() once the break has been processed.

Only in setups with "-o multiuser", cifs_sb_tlink() may fail, at which
point cifs_oplock_break() returns without putting the file reference,
mirroring the reference leak we already fixed in the companion patch to
cifs_queue_oplock_break().

This would trigger a crash due to busy inodes on the next unmount:

  BUG: Dentry ... still in use (1) [unmount of cifs cifs]
  VFS: Busy inodes after unmount of cifs (cifs)

Drop the reference on that path as well. Doing so before the out label
mirrors the normal path, which also puts the reference before
cifs_done_oplock_break().

Found by Sashiko code review. The failure path was not exercised at
runtime.

## Remediation

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

## Vendor advisories

- **Red Hat VEX** · Low · 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 2026-10-17 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-97556.json)