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CVE-2026-64136· NVD / CVE Program· CNA Linux

smb: client: protect tc_count increment in smb2_find_smb_sess_tcon_unlocked()

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().

CriticalCVSS 9.8 · v3.1—No exploit Fix available
Published
Jul 19, 2026
Updated
Aug 13, 2026
EPSS
0.5% · 40th percentile
CWE
—
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Report tools

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Action score

39

Monitor

Low priority for now.

CVSS
39 / 40 · 9.8 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.5%

CNA vs NVD score

NVD
—
CNA · Linux
9.8
NVD has not scored this yet; the score shown is the CNA’s.

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

Noroxi analysis

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Affected systems

VendorProduct
linuxlinux kernel

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

  • linux linux kernel6.6.128 and later · before 6.6.142
  • linux linux kernel6.12.75 and later · before 6.12.92
  • linux linux kernel6.18.16 and later · before 6.18.34
  • linux linux kernel6.19.6 and later · before 7.0.11
  • linux linux kernel7.1

Versions reported by the vendor

Affected version ranges reported by the assigning authority (Linux). Independent of NVD's CPE analysis and usually ahead of it.

  • Linux Linux

    • 8c59eeeeffa1524ef57e173a89a1a3ff539888d5, 7.0affected
    • 953953abb66e52c224057ab91e404284fefeab62 and later · before 7df1df6f40c0720d30206aa35c0343b962350e0daffected · git
    • 601dd3b79769b38d30b693c40afdb2a4b7edf9d0 and later · before 13fb413ae22a37c69341918a6d651d19a9b0b9b7affected · git
    • 3969db6b22e3d90d8c5f22ac1a7fe0350a94c136 and later · before bf4ebdb19ff9b3cdf992b50715fe61633327416aaffected · git
    • 96c4af418586ee9a6aab61738644366426e05316 and later · before e374f4e496fef8168784f93a4477d67be34485fdaffected · git
    • 96c4af418586ee9a6aab61738644366426e05316 and later · before 4d8690dace005a38e6dbde9ecce2da3ad85c7c41affected · git
    • 6.6.128 and later · before 6.6.142affected · semver
    • 6.12.75 and later · before 6.12.92affected · semver
    • 6.18.16 and later · before 6.18.34affected · semver
    • 6.19.6 and later · before 6.20affected · semver

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

EcosystemPackageAffected rangeFix
AlmaLinux:9kernelbefore 5.14.0-687.45.1.el9_85.14.0-687.45.1.el9_8
AlmaLinux:9kernel-64kbefore 5.14.0-687.45.1.el9_85.14.0-687.45.1.el9_8
AlmaLinux:9kernel-64k-corebefore 5.14.0-687.45.1.el9_85.14.0-687.45.1.el9_8
AlmaLinux:9kernel-64k-debugbefore 5.14.0-687.45.1.el9_85.14.0-687.45.1.el9_8
AlmaLinux:9kernel-64k-debug-corebefore 5.14.0-687.45.1.el9_85.14.0-687.45.1.el9_8
AlmaLinux:9kernel-64k-debug-develbefore 5.14.0-687.45.1.el9_85.14.0-687.45.1.el9_8
AlmaLinux:9kernel-64k-debug-devel-matchedbefore 5.14.0-687.45.1.el9_85.14.0-687.45.1.el9_8
AlmaLinux:9kernel-64k-debug-modulesbefore 5.14.0-687.45.1.el9_85.14.0-687.45.1.el9_8
AlmaLinux:9kernel-64k-debug-modules-corebefore 5.14.0-687.45.1.el9_85.14.0-687.45.1.el9_8
AlmaLinux:9kernel-64k-debug-modules-extrabefore 5.14.0-687.45.1.el9_85.14.0-687.45.1.el9_8
AlmaLinux:9kernel-64k-develbefore 5.14.0-687.45.1.el9_85.14.0-687.45.1.el9_8
AlmaLinux:9kernel-64k-devel-matchedbefore 5.14.0-687.45.1.el9_85.14.0-687.45.1.el9_8
AlmaLinux:9kernel-64k-modulesbefore 5.14.0-687.45.1.el9_85.14.0-687.45.1.el9_8
AlmaLinux:9kernel-64k-modules-corebefore 5.14.0-687.45.1.el9_85.14.0-687.45.1.el9_8
AlmaLinux:9kernel-64k-modules-extrabefore 5.14.0-687.45.1.el9_85.14.0-687.45.1.el9_8
AlmaLinux:9kernel-abi-stablelistsbefore 5.14.0-687.45.1.el9_85.14.0-687.45.1.el9_8
AlmaLinux:9kernel-corebefore 5.14.0-687.45.1.el9_85.14.0-687.45.1.el9_8
AlmaLinux:9kernel-cross-headersbefore 5.14.0-687.45.1.el9_85.14.0-687.45.1.el9_8
AlmaLinux:9kernel-debugbefore 5.14.0-687.45.1.el9_85.14.0-687.45.1.el9_8
AlmaLinux:9kernel-debug-corebefore 5.14.0-687.45.1.el9_85.14.0-687.45.1.el9_8
AlmaLinux:9kernel-debug-develbefore 5.14.0-687.45.1.el9_85.14.0-687.45.1.el9_8
AlmaLinux:9kernel-debug-devel-matchedbefore 5.14.0-687.45.1.el9_85.14.0-687.45.1.el9_8
AlmaLinux:9kernel-debug-modulesbefore 5.14.0-687.45.1.el9_85.14.0-687.45.1.el9_8
AlmaLinux:9kernel-debug-modules-corebefore 5.14.0-687.45.1.el9_85.14.0-687.45.1.el9_8

+96

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Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
Linux Linux13fb413ae22a37c69341918a6d651d19a9b0b9b7Vendor (CNA)
Linux Linux4d8690dace005a38e6dbde9ecce2da3ad85c7c41Vendor (CNA)
Linux Linux6.12.92Vendor (CNA)
Linux Linux6.18.34Vendor (CNA)
Linux Linux6.20Vendor (CNA)
Linux Linux6.6.142Vendor (CNA)
Linux Linux7df1df6f40c0720d30206aa35c0343b962350e0dVendor (CNA)
Linux Linuxbf4ebdb19ff9b3cdf992b50715fe61633327416aVendor (CNA)
Linux Linuxe374f4e496fef8168784f93a4477d67be34485fdVendor (CNA)
almalinux:kernel5.14.0-687.45.1.el9_8 · AlmaLinux:9Package registry (OSV)
almalinux:kernel-64k5.14.0-687.45.1.el9_8 · AlmaLinux:9Package registry (OSV)
almalinux:kernel-64k-core5.14.0-687.45.1.el9_8 · AlmaLinux:9Package registry (OSV)
almalinux:kernel-64k-debug5.14.0-687.45.1.el9_8 · AlmaLinux:9Package registry (OSV)
almalinux:kernel-64k-debug-core5.14.0-687.45.1.el9_8 · AlmaLinux:9Package registry (OSV)
almalinux:kernel-64k-debug-devel5.14.0-687.45.1.el9_8 · AlmaLinux:9Package registry (OSV)
almalinux:kernel-64k-debug-devel-matched5.14.0-687.45.1.el9_8 · AlmaLinux:9Package registry (OSV)
almalinux:kernel-64k-debug-modules5.14.0-687.45.1.el9_8 · AlmaLinux:9Package registry (OSV)
almalinux:kernel-64k-debug-modules-core5.14.0-687.45.1.el9_8 · AlmaLinux:9Package registry (OSV)
almalinux:kernel-64k-debug-modules-extra5.14.0-687.45.1.el9_8 · AlmaLinux:9Package registry (OSV)
almalinux:kernel-64k-devel5.14.0-687.45.1.el9_8 · AlmaLinux:9Package registry (OSV)
almalinux:kernel-64k-devel-matched5.14.0-687.45.1.el9_8 · AlmaLinux:9Package registry (OSV)
debian:linux6.12.94-1 · Debian:13Package registry (OSV)
red hat:kernel-64k-debug-debuginfo0:6.12.0-211.50.1.el10_2 · Red Hat:enterprise_linux:10.2Package registry (OSV)
red hat:kernel-64k-debug-devel0:6.12.0-211.50.1.el10_2 · Red Hat:enterprise_linux:10.2Package registry (OSV)
red hat:kernel-64k-debug-devel-matched0:6.12.0-211.50.1.el10_2 · Red Hat:enterprise_linux:10.2Package registry (OSV)
red hat:kernel-64k-debuginfo0:6.12.0-211.50.1.el10_2 · Red Hat:enterprise_linux:10.2Package registry (OSV)
red hat:kernel-64k-devel0:6.12.0-211.50.1.el10_2 · Red Hat:enterprise_linux:10.2Package registry (OSV)
red hat:kernel-64k-devel-matched0:6.12.0-211.50.1.el10_2 · Red Hat:enterprise_linux:10.2Package registry (OSV)
red hat:kernel-debug-debuginfo0:6.12.0-211.50.1.el10_2 · Red Hat:enterprise_linux:10.2Package registry (OSV)
red hat:kernel-debug-devel0:6.12.0-211.50.1.el10_2 · Red Hat:enterprise_linux:10.2Package registry (OSV)

+5

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

EPSS, last 120 days

FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

No commit or PR link among the references.

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

No credits in the CNA record.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

No nightly-computed relations.

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

Technical details

Attack conditions

  • Anyone who can reach it over the internet can trigger it.
  • No account or password is required.
  • No user action is required.
  • No special conditions are required; it is repeatable.

If successful

Confidentiality
high · data can be read
Integrity
high · data or configuration can be modified
Availability
high · the service can be disrupted
Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality impact
High
Integrity impact
High
Availability impact
High

Weakness class (CWE)

—

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

nvd-secondary

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

MITRE has no CAPEC/ATT&CK mapping for this CWE.

Change log

  1. Fix✗ → ✓

For records you follow, these changes also arrive as notifications. →

References

All records