CVE-2026-97443 perf/ftrace: Fix WARNING in __unregister_ftrace_function
A local attacker can trigger a kernel warning and potential instability by exploiting improper ftrace function unregistration during error cleanup paths.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-97443?
CVE-2026-97443 is a denial of service vulnerability in Linux, published on 24 Sep 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
In the Linux kernel, the following vulnerability has been resolved:
perf/ftrace: Fix WARNING in __unregister_ftrace_function
perf_ftrace_function_unregister() unconditionally calls unregister_ftrace_function() without checking whether the ftrace_ops was ever successfully registered. This triggers a WARN_ON in __unregister_ftrace_function() when the ops doesn't have FTRACE_OPS_FL_ENABLED set.
This can happen during perf_event_alloc() error cleanup when perf_trace_destroy() is called via __free_event() on an event whose ftrace_ops registration failed or was already torn down by perf_try_init_event()'s err_destroy path.
The call path is: perf_event_alloc() error cleanup -> __free_event() -> event->destroy() [tp_perf_event_destroy] -> perf_trace_destroy() -> perf_trace_event_close() -> TRACE_REG_PERF_CLOSE -> perf_ftrace_function_unregister() -> unregister_ftrace_function() -> __unregister_ftrace_function() -> WARN_ON(!(ops->flags & FTRACE_OPS_FL_ENABLED))
Fix this by checking FTRACE_OPS_FL_ENABLED before attempting to unregister. If the ops is not enabled, just free the filter and return success.
Which versions are affected by CVE-2026-97443?
How do I fix CVE-2026-97443?
Apply the vendor's patch.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-97443 being exploited?
There is no known exploitation of CVE-2026-97443 in the wild and no public exploit code.
Sources
Also known as AZL-103967, BELL-CVE-2026-97443, DEBIAN-CVE-2026-97443, GHSA-c83f-fgh5-9532, UBUNTU-CVE-2026-97443.