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Fencer Vulns
no cvss —

CVE-2026-97556 json

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

published 2026-09-25 44 d ago modified 2026-10-30 9 d ago also EUVD-2026-86864

cvss
—
not scored
cisa kev
Not listed
not in CISA's catalog
epss
0.2%
EPSS 0.2% chance of exploitation in 30 days, percentile 11%
public exploits
0
none known

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 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.

Patch / fix

  • Linux Linux 5.15.224, 6.1.189, 6.5, 6.6.158, 6.12.111, 6.18.53, 7.2.7, 7.3
  • linux Debian 12 6.1.190-1
  • linux Debian 13 6.12.111-1
  • linux Debian 14 7.2.7-1
  • linux-6.12 Debian 12 6.12.111-1~deb12u1

debian advisories DEBIAN-CVE-2026-97556

  • linux Ubuntu 26.04 LTS 7.0.0-42.42
  • linux-aws Ubuntu 26.04 LTS 7.0.0-1016.17
  • linux-gcp Ubuntu 26.04 LTS 7.0.0-1016.18
  • linux-ibm Ubuntu 26.04 LTS 7.0.0-1017.17
  • linux-riscv Ubuntu 26.04 LTS 7.0.0-42.42.1
  • linux-oracle Ubuntu 26.04 LTS 7.0.0-1015.16
  • linux-hwe-7.0 Ubuntu 24.04 LTS 7.0.0-42.42~24.04.1
  • linux-oem-7.0 Ubuntu 26.04 LTS 7.0.0-1017.17

ubuntu advisories UBUNTU-CVE-2026-97556

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • kernel-source Linux Micro 6.0 6.4.0-159998.55.1
  • kernel-default Linux Micro 6.0 6.4.0-159998.55.1
  • kernel-kvmsmall Linux Micro 6.0 6.4.0-159998.55.1
  • kernel-default-base Linux Micro 6.0 6.4.0-159998.55.1.159998.21.42
  • kernel-rt Linux Micro 6.2 6.12.0-160000.40.1
  • kernel-64kb SLES 16.0, Linux Micro 6.2, SLES for SAP applications 16.0 6.12.0-160000.40.1
  • kernel-source SLES 16.0, Linux Micro 6.2, SLES for SAP applications 16.0 6.12.0-160000.40.1
  • kernel-default SLES 16.0, SLE High Availability Extension 16.0, Linux Micro 6.2 +1 more 6.12.0-160000.40.1

suse advisories SUSE-SU-2026:24550-1SUSE-SU-2026:24422-1SUSE-SU-2026:24446-1SUSE-SU-2026:24437-1SUSE-SU-2026:24386-1

  • kernel-rt openSUSE Leap 16.0 6.12.0-160000.40.1
  • dtb-aarch64 openSUSE Leap 16.0 6.12.0-160000.40.1
  • kernel-64kb openSUSE Leap 16.0 6.12.0-160000.40.1
  • kernel-syms openSUSE Leap 16.0 6.12.0-160000.40.1
  • kernel-azure openSUSE Leap 16.0 6.12.0-160000.40.1
  • kernel-obs-qa openSUSE Leap 16.0 6.12.0-160000.40.1
  • kernel-source openSUSE Leap 16.0 6.12.0-160000.40.1
  • kernel-default openSUSE Leap 16.0 6.12.0-160000.40.1

opensuse advisories openSUSE-SU-2026:22167-1openSUSE-SU-2026:12074-1

  • kernel Azure Linux 3.0 6.6.158.1-1

azure linux advisories AZL-104327

Azure Linux vulnerability data, Copyright (c) Microsoft Corporation, from https://github.com/microsoft/AzureLinuxVulnerabilityData via OSV, under the MIT licence; changed: normalised to fixed package versions per release. MIT

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-97556 updated cvss 5.5

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

  • Red Hat Enterprise Linux 9 rv, perf, rtla, kernel, bpftool, libperf, +82 more Red Hat Enterprise Linux 10 kernel Red Hat OpenShift Container Platform 4 openshift/ose-rhel-coreos-9 Red Hat OpenShift Container Platform 5 openshift/ose-rhel-coreos-9
    affected: workaround, no fix available “Fix deferred”
  • Red Hat Enterprise Linux 6 perf, kernel, python-perf, kernel-kdump, kernel-firmware, kernel-bootwrapper, +1 more Red Hat Enterprise Linux 7 perf, kernel, bpftool, kernel-rt, python-perf, kernel-kdump, +8 more Red Hat Enterprise Linux 8 perf, kernel, bpftool, kernel-rt, kernel-core, kernel-tools, +29 more Red Hat Enterprise Linux 9 kernel-rt, kernel-rt-selftests-internal Red Hat OpenShift Container Platform 4 openshift/ose-rhel-coreos-8
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

Exploit prediction

0.21% chance of exploitation in the next 30 days, higher than 11% of all scored CVEs (FIRST EPSS, 2026-11-08).

Affected products

  • Linux Linux

Classification

Technology feeds

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.