Critical

CVE-2026-64136 — 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().

Published Jul 19, 2026 · Updated Oct 15, 2026 · Sources: NIST National Vulnerability Database, CVE Program (cve.org) e CISA ADP · CNA: Linux

Low

Who exploits it and how urgent it is

A 0–100 score combining confirmed exploitation, ransomware and APT use, public exploits, EPSS and severity.

No exploitation signal in the sources consulted so far.

How the score was calculated

Technical severity (critical)+10

The score orders the patch queue; it does not replace your asset context (internet exposure, criticality, compensating controls).

Triage

Is it exploited, how likely is exploitation, what does it touch, and how severe do the sources call it.

Exploitation

Not confirmed

Not in CISA KEV — an absence of record, not proof it is unexploited.

EPSS FIRST

—

No EPSS score.

Affects

Linux

Linux and 1 more

CVSS base

9.8

Critical · 2 source(s)

Remediation

Fixes and mitigations documented by the sources — linked to the original advisory.

Documented patch — git.kernel.org (NIST National Vulnerability Database)
Documented patch — git.kernel.org (NIST National Vulnerability Database)
Documented patch — git.kernel.org (NIST National Vulnerability Database)
Documented patch — git.kernel.org (NIST National Vulnerability Database)
Documented patch — git.kernel.org (NIST National Vulnerability Database)

First 24 hours

Ordered from the record’s own fields — exposure first, because you cannot patch what you have not found. A rule-generated starting point.

Identify exposed assets running the affected vendor/product/version combinations (Linux Linux, Linux Linux Kernel).
The attack is network-based and needs no privileges: restrict exposure (ACLs, VPN, WAF) until patched.
Apply the fixed version or the patch documented under Remediation.
Search available logs for exploit probes, errors and authentication anomalies.

Affected scope

Vendor, product and versions as the sources word them.

Vendor	Product	Versions	Status	Source
Linux	Linux	≥ 601dd3b79769b38d30b693c40afdb2a4b7edf9d0 and < 13fb413ae22a37c69341918a6d651d19a9b0b9b7version 7.0≥ 6.19.6 and < 6.20≥ 6.18.16 and < 6.18.34≥ 6.12.75 and < 6.12.92≥ 6.6.128 and < 6.6.142version 8c59eeeeffa1524ef57e173a89a1a3ff539888d5≥ 96c4af418586ee9a6aab61738644366426e05316 and < 4d8690dace005a38e6dbde9ecce2da3ad85c7c41 and 3 more ≥ 96c4af418586ee9a6aab61738644366426e05316 and < e374f4e496fef8168784f93a4477d67be34485fd≥ 3969db6b22e3d90d8c5f22ac1a7fe0350a94c136 and < bf4ebdb19ff9b3cdf992b50715fe61633327416a≥ 953953abb66e52c224057ab91e404284fefeab62 and < 7df1df6f40c0720d30206aa35c0343b962350e0d	Vulnerable	CVE Program (cve.org) e CISA ADP
Linux	Linux Kernel	≥ 6.6.128 and < 6.6.142version 7.1-rc4version 7.1-rc3version 7.1-rc2version 7.1-rc1≥ 6.19.6 and < 7.0.11≥ 6.18.16 and < 6.18.34≥ 6.12.75 and < 6.12.92	Vulnerable	NIST National Vulnerability Database

Attack characteristics

The CVSS vector, decoded. It describes the attack, not your exposure to it.

Attack vector

Network

Attack complexity

Low

Privileges required

None

User interaction

None

Scope

Unchanged

Confidentiality

High

Integrity

High

Availability

High

Every base score collected

Sources score independently and may disagree; each row says who scored it and under which version.

Score	Version	Severity	Expl.	Impact	Scored by
9.8	CVSS 3.1	Critical	3.9	5.9	416baaa9-dc9f-4396-8d5f-8c081fb06d67 via NIST National Vulnerability Database
9.8	CVSS 3.1	Critical	—	—	Linux via CVE Program (cve.org) e CISA ADP

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H (score shown at the top: 416baaa9-dc9f-4396-8d5f-8c081fb06d67)

Detection

Read off the CVSS vector and the weakness class. Starting points, not tested rules.

Prioritize edge telemetry for the network-reachable component (proxy, WAF, IDS/IPS).

web/proxy/WAF logsnetwork IDS/IPS

Timeline

What happened to this CVE, newest first.

2026
Affected products added · linux/linux
Oct 15, 2026 · CVE Program (cve.org) e CISA ADP
Record published
Oct 15, 2026
Fix documented
Oct 15, 2026 · NIST National Vulnerability Database
CVSS changed · 9.8
Oct 15, 2026 · NIST National Vulnerability Database
Source status changed · → Analyzed
Oct 15, 2026 · NIST National Vulnerability Database
Record created in this database
Oct 15, 2026 · NIST National Vulnerability Database
CVE published
Jul 19, 2026 · Linux

Source activity

Repeated readings are counted rather than listed.

1× Official description updated · Oct 15, 2026 – Oct 15, 2026

References

5 on the record

git.kernel.org/stable/c/13fb413ae22a37c69341918a6d651d19a9b0b9b7
Patch, NIST National Vulnerability Database
git.kernel.org/stable/c/e374f4e496fef8168784f93a4477d67be34485fd
Patch, NIST National Vulnerability Database
git.kernel.org/stable/c/4d8690dace005a38e6dbde9ecce2da3ad85c7c41
Patch, NIST National Vulnerability Database
git.kernel.org/stable/c/bf4ebdb19ff9b3cdf992b50715fe61633327416a
Patch, NIST National Vulnerability Database
git.kernel.org/stable/c/7df1df6f40c0720d30206aa35c0343b962350e0d
Patch, NIST National Vulnerability Database

Elsewhere on this site

Linux
every CVE for this vendor

Related CVEs (same products)

Critical CVE-2026-99999 ipv4: validate checksum_start before completing checksum 10h
Unknown CVE-2026-98432 ipv4: free inet_opt and ireq_opt after an RCU grace period 10h
Unknown CVE-2026-98424 wifi: cfg80211: undo netns switch if renaming the wiphy fails 1d
Unknown CVE-2026-98425 wifi: mac80211: don't warn when an IBSS has no channel to scan 1d
Unknown CVE-2026-98426 wifi: mwifiex: fix IRQ leak using wrong index in MSI-X error path 1d
Unknown CVE-2026-98427 net/sched: codel: bound the dropping loop per dequeue call 1d

Not in any source we poll

Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.

No FIRST EPSS score.
No CISA SSVC assessment.
No CWE classification.
No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
No exploit packet captures, log samples, or incident case IDs supplied.

Answered from this record

Text assembled only from the fields above — no additional claims.

What should defenders know first?

CVE-2026-64136 is "smb: client: protect tc_count increment in smb2_find_smb_sess_tcon_unlocked()", rated Critical. It affects Linux (Linux); versions are in the scope table. It is not in CISA KEV, which does not rule out exploitation. CVSS 9.8 describes technical severity. First verify whether exposed or business-critical assets run the affected versions, apply vendor fixes or mitigations, and preserve logs for review.

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