CVE-2026-64389
ksmbd NTLMv2 flaw allows session-key tampering during failed auth (SMB3 multichannel)
Is CVE-2026-64389 being exploited?
Not confirmed. CVE-2026-64389 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 0.45% probability of exploitation in the next 30 days.
How severe is CVE-2026-64389?
CVE-2026-64389 is rated High with a CVSS score of 8.2. 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-2026-64389?
Yes. A fix has been recorded for CVE-2026-64389. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-64389 affect?
CVE-2026-64389 affects Linux kernel ksmbd (SMB server), SMB3 multichannel setups, Linux distributions with ksmbd enabled. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-64389?
Apply kernel updates or disable ksmbd/SMB multichannel until patched
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Attackers can alter session keys before verification, enabling session hijack and unauthorized access to SMB shares.
Patch when possible
- affected>= e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 and < b56400364aed5c34d6e1a0b493081290a5328a9c
- affected>= e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 and < 89ca7756d5566ba636bb9092cdbe57dab095e136
- affected>= e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 and < 954d196bebb2b50151cb96454c72dc113b2af1ac
- 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.