CVE-2026-64400
ksmbd path traversal lets SMB write users escape share roots.
Is CVE-2026-64400 being exploited?
Not confirmed. CVE-2026-64400 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 0.36% probability of exploitation in the next 30 days.
How severe is CVE-2026-64400?
CVE-2026-64400 is rated High with a CVSS score of 8.6. 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-2026-64400?
Yes. A fix has been recorded for CVE-2026-64400. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-64400 affect?
CVE-2026-64400 affects Linux kernel (ksmbd SMB server), Systems with ksmbd caseless mode enabled, Linux SMB/CIFS file shares. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-64400?
Update kernel to fixed version; or disable ksmbd caseless mode and restrict SMB write access.
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Authenticated SMB clients with write permissions can bypass share boundary to create files/dirs outside exports, enabling tampering, persistence, or escalation.
Patch when possible
- affected>= 74d7970febf7e9005375aeda0df821d2edffc9f7 and < 8c9a4f1327eb71efbf14842e7b8a6d965077eb67
- affected>= 74d7970febf7e9005375aeda0df821d2edffc9f7 and < 54bab9ba5a9f156ffa9324fcbe5a356fd0242f95
- affected019aae488dbc67c97a33db03652e20e2c9e3afa7
- affected6927ffe7479c72e7ebf885507227266a75f7c97d
- affectedef6cc1c465786b3e4e735d1ab8b616b3e94402df
- affected>= 5.15.145 and < 5.16
- affected>= 6.1.71 and < 6.2
- affected>= 6.3.10 and < 6.4
- affected6.4
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.