CVE-2026-64398
Authenticated SMB client can zero file data via ksmbd FSCTL_SET_ZERO_DATA permission bypass.
Is CVE-2026-64398 being exploited?
Not confirmed. CVE-2026-64398 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 0.46% probability of exploitation in the next 30 days.
How severe is CVE-2026-64398?
CVE-2026-64398 is rated High with a CVSS score of 8.1. 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-2026-64398?
Yes. A fix has been recorded for CVE-2026-64398. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-64398 affect?
CVE-2026-64398 affects Linux kernel ksmbd (in-kernel SMB server), Kernels with ksmbd prior to the FSCTL_SET_ZERO_DATA fix (e.g., around 7.1-rc7). Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-64398?
Update kernel/ksmbd to the patched release or apply upstream commit immediately.
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Authenticated SMB client can zero/overwrite file contents without FILE_WRITE_DATA, causing data corruption or loss on affected hosts.
Immediate action required
- affected>= e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 and < 25377f369688dd0bd814dc8965ed26d44238ecaa
- affected>= e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 and < 3072d82461f498c85daea8766e9d8bfbada31605
- affected>= e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 and < ca53bb17f4e8232cfaece3953d3cef62c559b039
- affected>= e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 and < 57f2042fd87d7ce8fc3ac8b6c176e554df68b1a7
- affected>= e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 and < deffa929086d7902e30918adf3dd27ccfe9c08b1
- affected>= e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 and < 3320ba068198adc144c89d6661b805acce01735b
- 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.