Kernel-level SMB server (ksmbd) bug causes kernel memory corruption; affects Linux file servers/NAS widely used in enterprises, with potential for crash or kernel compromise.
CVE-2026-89635
Linux ksmbd durable-handle reconnect UAF leading to kernel compromise
Is CVE-2026-89635 being exploited?
Not confirmed. CVE-2026-89635 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 0.55% probability of exploitation in the next 30 days.
How severe is CVE-2026-89635?
CVE-2026-89635 is rated Critical with a CVSS score of 9.8. 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-2026-89635?
Yes. A fix has been recorded for CVE-2026-89635. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-89635 affect?
CVE-2026-89635 affects Linux kernel (ksmbd SMB server), SMB file servers, NAS devices using in-kernel ksmbd. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-89635?
Apply vendor kernel updates with ksmbd fixes; restrict SMB access until patched.
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Authenticated SMB client can trigger a kernel use-after-free during durable-handle reconnect, causing kernel crash, privilege escalation, or potential RCE.
Immediate action required
- affected>= f363a0fb134a3eb9e47368b1edbd251fd76be84b and < 74e3ef4630f004c0de40c0540648a5a4033c6c9d
- affected>= f363a0fb134a3eb9e47368b1edbd251fd76be84b and < 3f220a0a62e6b9b391c9d1f0e6580b05173cc7f7
- affected7.2
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.