CVE-2026-64396
Use-after-free in Linux ksmbd SMB2 lock cancellation enabling kernel crash or root compromise
Is CVE-2026-64396 being exploited?
Not confirmed. CVE-2026-64396 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 0.43% probability of exploitation in the next 30 days.
How severe is CVE-2026-64396?
CVE-2026-64396 is rated High with a CVSS score of 8.8. 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-2026-64396?
Yes. A fix has been recorded for CVE-2026-64396. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-64396 affect?
CVE-2026-64396 affects Linux kernel ksmbd (SMB server), Linux distributions with ksmbd enabled, Servers exposing SMB (TCP/445). Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-64396?
Apply vendor/kernel updates immediately and restrict/block SMB (TCP/445) until patched.
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Remote SMB clients sending crafted lock requests can trigger a kernel use-after-free, causing DoS or potential arbitrary code execution as root.
Patch when possible
- affected>= e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 and < 367c42a611fe488b7b03f1f6737f4dee0e8b20a2
- affected>= e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 and < 7703fd9aba1f2483c8e55f9ff73b7663e0761ed9
- affected>= e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 and < 463bbd79698513af4dad50fe1c573825f297ca2e
- affected>= e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 and < 5aa1cb01155f96824003baf7997cdf1f150caba3
- affected>= e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 and < 5c75275c0fc9a2deb0d8f5604edcb16f288171c8
- affected>= e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 and < d20d1c8ba5765d1d12eefc0aee6385ab3f240e1e
- 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.