CVE-2026-64451 is a Linux kernel vulnerability in the tracing subsystem where func_set_flag() dereferences tr->current_trace_flags without first confirming that the active tracer is the function tracer. If the active tracer changes to a different tracer (e.g., wakeup_rt), current_trace_flags becomes NULL. Subsequent writes to function tracer option files cause func_set_flag() to dereference this NULL pointer, resulting in a kernel crash. The fix involves moving the check of the current tracer before dereferencing current_trace_flags to avoid the NULL pointer dereference.

This vulnerability causes a NULL pointer dereference leading to a kernel crash (denial of service) when writing to function tracer option files after the active tracer has switched away from the function tracer. There is no indication of code execution or privilege escalation from the provided data.

A fix is available that reorders the check in func_set_flag() to prevent dereferencing a NULL pointer. Users should apply the official Linux kernel patch that addresses this issue. Patch status is not explicitly confirmed in the input data; therefore, check the vendor advisory for current remediation guidance.