smb: client: protect tc_count increment in smb2_find_smb_sess_tcon_unlocked() (CVE-2026-64136) | HOL Guard CVE

Critical · CVSS 9.8CVE-2026-64136

smb: client: protect tc_count increment in smb2_find_smb_sess_tcon_unlocked()

Answer in brief

CVE-2026-64136 records a Critical severity (CVSS 9.8) vulnerability in smb: client: protect tc_count increment in smb2_find_smb_sess_tcon_unlocked(). The current sources do not mark it as known exploited. The current feed maps Linux/Linux (generic), Linux/Linux (generic). Check affected ranges and fixed versions before updating.

Analysis pending evidence review

HOL Guard separates source facts from reviewed analysis. See the methodology.

Published Jul 19, 2026Updated Aug 13, 2026Source checked Sep 20, 2026First seen by HOL Aug 5, 2026Material review Aug 13, 2026

Upstream Advisory

Key facts

Risk: Critical · CVSS 9.8
Exploitation: Not marked as known exploited
Affected software: 7 mapped packages or products
Fix availability: Available

Why this deserves its current priority

CVSS is 9.8. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.

Analysis status

Analysis pending evidence review

Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.

Affected scope and exposure questions

The current feed maps Linux/Linux (generic), Linux/Linux (generic). Check affected ranges and fixed versions before updating.

Affected products and reported versions
Product	Affected versions	Fixed versions
cpe:2.3:o:linux:linux_kernel::::::::	Not reported	Not reported
cpe:2.3:o:linux:linux_kernel:7.1:rc1::::::	Not reported	Not reported
cpe:2.3:o:linux:linux_kernel:7.1:rc2::::::	Not reported	Not reported
cpe:2.3:o:linux:linux_kernel:7.1:rc3::::::	Not reported	Not reported
cpe:2.3:o:linux:linux_kernel:7.1:rc4::::::	Not reported	Not reported

Mapped affected packages and fixed versions
Package	Affected range	Fixed version
Linux/Linuxgeneric	>=953953abb66e52c224057ab91e404284fefeab62 <7df1df6f40c0720d30206aa35c0343b962350e0d \|\| >=601dd3b79769b38d30b693c40afdb2a4b7edf9d0 <13fb413ae22a37c69341918a6d651d19a9b0b9b7 \|\| >=3969db6b22e3d90d8c5f22ac1a7fe0350a94c136 <bf4ebdb19ff9b3cdf992b50715fe61633327416a \|\| >=96c4af418586ee9a6aab61738644366426e05316 <e374f4e496fef8168784f93a4477d67be34485fd \|\| >=96c4af418586ee9a6aab61738644366426e05316 <4d8690dace005a38e6dbde9ecce2da3ad85c7c41 \|\| 8c59eeeeffa1524ef57e173a89a1a3ff539888d5 \|\| >=6.6.128 <6.6.142 \|\| >=6.12.75 <6.12.92 \|\| >=6.18.16 <6.18.34 \|\| >=6.19.6 <6.20	7df1df6f40c0720d30206aa35c0343b962350e0d, 13fb413ae22a37c69341918a6d651d19a9b0b9b7, bf4ebdb19ff9b3cdf992b50715fe61633327416a, e374f4e496fef8168784f93a4477d67be34485fd, 4d8690dace005a38e6dbde9ecce2da3ad85c7c41, 6.6.142, 6.12.92, 6.18.34, 6.20
Linux/Linuxgeneric	7.0	Not reported

Recommended response

Check inventory. Check lockfiles and deployed manifests for Linux/Linux, Linux/Linux.
Review the reported fix. Update Linux/Linux to 7df1df6f40c0720d30206aa35c0343b962350e0d if you use the affected versions. Test the change in a non-production environment first.

Evidence timeline and material changes

Published upstream
Jul 19, 2026
Evidence: source:cvelist:source_dates:source-dates:record
Source modified
Aug 13, 2026
Evidence: source:cvelist:source_dates:source-dates:record
First seen by HOL
Aug 5, 2026

Sources and claim methodology

Upstream source description

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().

Quoted source text, attributed separately from HOL analysis.