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Fencer Vulns
critical 9.8

CVE-2026-64136 in the critical feed json

smb: client: protect tc_count increment in smb2_find_smb_sess_tcon_unlocked()

published 2026-07-19 3 mo ago modified 2026-10-30 9 d ago also EUVD-2026-45821

cvss
9.8
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.4%
EPSS 0.4% chance of exploitation in 30 days, percentile 35%
public exploits
0
none known

Summary

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

smb: client: protect tc_count increment in smb2_find_smb_sess_tcon_unlocked()

Commit 96c4af418586 ("cifs: Fix locking usage for tcon fields") refactored cifs code to change cifs_tcp_ses_lock for tc_lock around tc_count changes.

There was missing lock around tc_count increment inside smb2_find_smb_sess_tcon_unlocked().

Patch / fix

  • Linux Linux 6.6.142, 6.12.92, 6.18.34, 6.20, 7.0.11, 7.1
  • linux Debian 13 6.12.94-1
  • linux Debian 14 7.0.12-1

debian advisories DEBIAN-CVE-2026-64136

  • linux Ubuntu 24.04 LTS 6.8.0-139.139
  • linux Ubuntu 26.04 LTS 7.0.0-28.28
  • linux-aws Ubuntu 24.04 LTS 6.8.0-1064.67
  • linux-aws Ubuntu 26.04 LTS 7.0.0-1009.9
  • linux-gcp Ubuntu 24.04 LTS 6.8.0-1067.75
  • linux-gcp Ubuntu 26.04 LTS 7.0.0-1008.8
  • linux-gke Ubuntu 24.04 LTS 6.8.0-1062.70
  • linux-gke Ubuntu 26.04 LTS 7.0.0-1003.4

ubuntu advisories UBUNTU-CVE-2026-64136

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 RHEL 9 5.14.0-687.45.1.el9_8
  • rv RHEL 9 5.14.0-687.45.1.el9_8
  • perf RHEL 9 5.14.0-687.45.1.el9_8
  • rtla RHEL 9 5.14.0-687.45.1.el9_8
  • libperf RHEL 9 5.14.0-687.45.1.el9_8
  • kernel-rt RHEL 9 5.14.0-687.45.1.el9_8
  • kernel-64k RHEL 9 5.14.0-687.45.1.el9_8
  • kernel-core RHEL 9 5.14.0-687.45.1.el9_8

red hat advisories RHSA-2026:64808RHSA-2026:61887

  • kernel-64kb SLE Module for Basesystem 15 SP7 6.4.0-150700.53.81.1
  • kernel-syms SLE Module for Development Tools 15 SP7 6.4.0-150700.53.81.1
  • kernel-azure SLE Module for Public Cloud 15 SP7 6.4.0-150700.53.81.1
  • kernel-source SLE Module for Development Tools 15 SP7, SLE Module for Basesystem 15 SP7 6.4.0-150700.53.81.1
  • kernel-default SLE Workstation Extension 15 SP7, SLE Module for Legacy 15 SP7, SLE Module for Basesystem 15 SP7 +2 more 6.4.0-150700.53.81.1
  • kernel-zfcpdump SLE Module for Basesystem 15 SP7 6.4.0-150700.53.81.1
  • kernel-obs-build SLE Module for Development Tools 15 SP7 6.4.0-150700.53.81.1
  • kernel-default-base SLE Module for Basesystem 15 SP7 6.4.0-150700.53.81.1.150700.17.45.1

suse advisories SUSE-SU-2026:4254-1SUSE-SU-2026:4120-1

  • kernel AlmaLinux 9 5.14.0-687.45.1.el9_8
  • rv AlmaLinux 9 5.14.0-687.45.1.el9_8
  • perf AlmaLinux 9 5.14.0-687.45.1.el9_8
  • rtla AlmaLinux 9 5.14.0-687.45.1.el9_8
  • libperf AlmaLinux 9 5.14.0-687.45.1.el9_8
  • kernel-rt AlmaLinux 9 5.14.0-687.45.1.el9_8
  • kernel-64k AlmaLinux 9 5.14.0-687.45.1.el9_8
  • kernel-core AlmaLinux 9 5.14.0-687.45.1.el9_8

almalinux advisories ALSA-2026:64808ALSA-2026:61887

  • kernel Rocky Linux 9 5.14.0-687.45.1.el9_8
  • kernel Rocky Linux 10 6.12.0-211.50.1.el10_2

rocky linux advisories RLSA-2026:64808RLSA-2026:61887

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-2026-64136 updated cvss 7.0

kernel: smb: client: protect tc_count increment in smb2_find_smb_sess_tcon_unlocked()

  • Red Hat Enterprise Linux AppStream (v. 9) rv 5.14.0-687.45.1.el9_8, perf 5.14.0-687.45.1.el9_8, rtla 5.14.0-687.45.1.el9_8, python3-perf 5.14.0-687.45.1.el9_8, kernel-devel-matched 5.14.0-687.45.1.el9_8, kernel-64k-devel-matched 5.14.0-687.45.1.el9_8, +7 more
    fixed: vendor fix RHSA-2026:64808
  • Red Hat Enterprise Linux AppStream (v. 10) rv 6.12.0-211.50.1.el10_2, perf 6.12.0-211.50.1.el10_2, rtla 6.12.0-211.50.1.el10_2, python3-perf 6.12.0-211.50.1.el10_2, kernel-devel-matched 6.12.0-211.50.1.el10_2, kernel-64k-devel-matched 6.12.0-211.50.1.el10_2, +7 more
    fixed: vendor fix RHSA-2026:61887
  • Red Hat Enterprise Linux BaseOS (v. 9) kernel 5.14.0-687.45.1.el9_8, kernel-64k 5.14.0-687.45.1.el9_8, kernel-core 5.14.0-687.45.1.el9_8, kernel-tools 5.14.0-687.45.1.el9_8, kernel-modules 5.14.0-687.45.1.el9_8, kernel-64k-core 5.14.0-687.45.1.el9_8, +27 more
    fixed: vendor fix RHSA-2026:64808
  • Red Hat Enterprise Linux BaseOS (v. 10) kernel 6.12.0-211.50.1.el10_2, kernel-64k 6.12.0-211.50.1.el10_2, kernel-core 6.12.0-211.50.1.el10_2, kernel-tools 6.12.0-211.50.1.el10_2, kernel-modules 6.12.0-211.50.1.el10_2, kernel-64k-core 6.12.0-211.50.1.el10_2, +28 more
    fixed: vendor fix RHSA-2026:61887
  • Red Hat Enterprise Linux CodeReady Linux Builder (v. 9) libperf 5.14.0-687.45.1.el9_8, kernel-debuginfo-common-s390x 5.14.0-687.45.1.el9_8, kernel-debuginfo-common-x86_64 5.14.0-687.45.1.el9_8, kernel-debuginfo-common-aarch64 5.14.0-687.45.1.el9_8, kernel-debuginfo-common-ppc64le 5.14.0-687.45.1.el9_8
    fixed: vendor fix RHSA-2026:64808
  • Red Hat Enterprise Linux CodeReady Linux Builder (v. 10) libperf 6.12.0-211.50.1.el10_2, kernel-debuginfo-common-s390x 6.12.0-211.50.1.el10_2, kernel-debuginfo-common-x86_64 6.12.0-211.50.1.el10_2, kernel-debuginfo-common-aarch64 6.12.0-211.50.1.el10_2, kernel-debuginfo-common-ppc64le 6.12.0-211.50.1.el10_2
    fixed: vendor fix RHSA-2026:61887
  • Red Hat Enterprise Linux Real Time (v. 9) kernel-rt 5.14.0-687.45.1.el9_8, kernel-rt-64k 5.14.0-687.45.1.el9_8, kernel-rt-core 5.14.0-687.45.1.el9_8, kernel-rt-modules 5.14.0-687.45.1.el9_8, kernel-rt-64k-core 5.14.0-687.45.1.el9_8, kernel-rt-debug-core 5.14.0-687.45.1.el9_8, +14 more
    fixed: vendor fix RHSA-2026:64808
  • Red Hat Enterprise Linux Real Time (v. 10) kernel-rt 6.12.0-211.50.1.el10_2, kernel-rt-64k 6.12.0-211.50.1.el10_2, kernel-rt-core 6.12.0-211.50.1.el10_2, kernel-rt-modules 6.12.0-211.50.1.el10_2, kernel-rt-64k-core 6.12.0-211.50.1.el10_2, kernel-rt-debug-core 6.12.0-211.50.1.el10_2, +14 more
    fixed: vendor fix RHSA-2026:61887
show 3 more
  • Red Hat Enterprise Linux Real Time for NFV (v. 9) kernel-rt 5.14.0-687.45.1.el9_8, kernel-rt-core 5.14.0-687.45.1.el9_8, kernel-rt-modules 5.14.0-687.45.1.el9_8, kernel-rt-debug-core 5.14.0-687.45.1.el9_8, kernel-rt-modules-core 5.14.0-687.45.1.el9_8, kernel-rt-debug-modules 5.14.0-687.45.1.el9_8, +4 more
    fixed: vendor fix RHSA-2026:64808
  • Red Hat Enterprise Linux Real Time for NFV (v. 10) kernel-rt 6.12.0-211.50.1.el10_2, kernel-rt-core 6.12.0-211.50.1.el10_2, kernel-rt-modules 6.12.0-211.50.1.el10_2, kernel-rt-debug-core 6.12.0-211.50.1.el10_2, kernel-rt-modules-core 6.12.0-211.50.1.el10_2, kernel-rt-debug-modules 6.12.0-211.50.1.el10_2, +4 more
    fixed: vendor fix RHSA-2026:61887
  • 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-kvm, kernel-rt-core, kernel-rt-modules, kernel-rt-debug-kvm, kernel-rt-debug-core, +12 more
    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

CISA SSVC

Exploitation
none
Automatable
yes
Technical impact
total
Assessed
23 d ago

Exploit prediction

0.41% chance of exploitation in the next 30 days, higher than 35% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 9.8 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Affected products

  • Linux Linux

Classification

Weakness
  • CWE-362 Concurrent Execution using Shared Resource with Improper Synchronization
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.