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

Severity: critical (CVSS 9.8 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.4% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-07-19 · updated 2026-10-30
Weakness: CWE-362

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().

Affected products

Linux kernel: from 6.6.128 before 6.6.142; from 6.12.75 before 6.12.92; from 6.18.16 before 6.18.34; from 6.19.6 before 7.0.11; 7.1-rc1, 7.1-rc2, 7.1-rc3, 7.1-rc4 — fixed in 6.6.142, 6.12.92, 6.18.34, 7.0.11
Linux: from 6.6.128 before 6.6.142; from 6.12.75 before 6.12.92; from 6.18.16 before 6.18.34; from 6.19.6 before 6.20 — fixed in 6.6.142, 6.12.92, 6.18.34, 6.20

How to fix

Upgrade to a fixed version: Linux kernel 6.6.142, 6.12.92, 6.18.34, 7.0.11; Linux 6.6.142, 6.12.92, 6.18.34, 6.20. Check the vendor advisory for mitigations.

References

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