CVE-2026-64138
ksmbd ACL SID validation flaw allows SMB ACL bypass or privilege escalation
Is CVE-2026-64138 being exploited?
Not confirmed. CVE-2026-64138 does not appear in CISA's Known Exploited Vulnerabilities catalog, which records only exploitation that has been observed and reported publicly. That is evidence of absence of a report, not evidence the flaw is unattacked. EPSS currently estimates a 0.41% probability of exploitation in the next 30 days.
How severe is CVE-2026-64138?
CVE-2026-64138 is rated High. Severity describes how bad exploitation would be, not how likely it is: pair it with exploitation evidence before deciding what to patch first.
Is there a patch for CVE-2026-64138?
Yes. A fix has been recorded for CVE-2026-64138. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-64138 affect?
CVE-2026-64138 affects Linux kernel with ksmbd (SMB server), Servers exposing SMB/CIFS, VMs/containers relying on host kernel ksmbd. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-64138?
Install kernel update, restart ksmbd/SMB, restrict SMB exposure
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
ACL validation flaw in ksmbd lets crafted SMB requests bypass ACL inheritance, enabling unauthorized file access or privilege escalation.
Patch when possible
- affected>= e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 and < f0e5c9c663badc9982e6941322eef1cb17de0f11
- affected>= e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 and < 18d8db24b0a5b7be4829238dd4022236df02d421
- affected>= e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 and < 1c9d0646a9959752f11ca1080dc1ff26bd1756cb
- affected>= e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 and < 69f030cf95488ae1186c72ac8c66fd279664ea7f
- affected5.15
As published in the CVE Program record. A version outside these ranges is not a statement that it is unaffected — vendors sometimes understate a range, and distribution-backported builds carry upstream numbers that do not reflect what was patched into them.