CVE-2026-64390
Use-after-free in Linux ksmbd SMB LOCK handling via SMB3 multichannel
Is CVE-2026-64390 being exploited?
Not confirmed. CVE-2026-64390 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 0.47% probability of exploitation in the next 30 days.
How severe is CVE-2026-64390?
CVE-2026-64390 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-2026-64390?
Yes. A fix has been recorded for CVE-2026-64390. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-64390 affect?
CVE-2026-64390 affects Linux kernel (ksmbd SMB server module), Systems using SMB3 multichannel with ksmbd enabled, Linux distributions shipping or backporting ksmbd. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-64390?
Install vendor kernel updates and reboot affected hosts
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Use-after-free in ksmbd allowing kernel memory corruption from remote SMB clients, enabling DoS, privilege escalation, or potential RCE.
Immediate action required
- affected>= f5a544e3bab78142207e0242d22442db85ba1eff and < 22d38cf75b556c20b039743bdf3654d535b858be
- affected>= f5a544e3bab78142207e0242d22442db85ba1eff and < 66eb3643164e5e1029907793926c132f8b5c6148
- affected>= f5a544e3bab78142207e0242d22442db85ba1eff and < ea5c9bf99f626a15cc59f645dc895f2b3f01992e
- affected>= f5a544e3bab78142207e0242d22442db85ba1eff and < fe20d492a69a6f79e637f438072b212e21ed3b78
- affected>= f5a544e3bab78142207e0242d22442db85ba1eff and < 427faaa52b0b399940c1a88065a5c310d10dad15
- affected>= f5a544e3bab78142207e0242d22442db85ba1eff and < 5fecc15a30cb9ebd310f7b52c1ab607edcea78f6
- affected>= f5a544e3bab78142207e0242d22442db85ba1eff and < c1016dd1d8b2bcd1158bbaabe94a31bb7e7431fb
- 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.