# 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.

- **Severity:** Not scored
- **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:** Yes
- **Published:** 24 Sep 2026
- **Updated:** 25 Sep 2026
- **Also known as:** AZL-103967, BELL-CVE-2026-97443, DEBIAN-CVE-2026-97443, GHSA-c83f-fgh5-9532, UBUNTU-CVE-2026-97443

## 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.

## Is CVE-2026-97443 being exploited?

There is no known exploitation of CVE-2026-97443 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-97443 and fix it if it is affected.

What it is: 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.
Exploitation: There is no known exploitation of CVE-2026-97443 in the wild and no public exploit code.

Affected product: Linux. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-97443/ (Markdown: https://insights.sbomify.com/CVE-2026-97443/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-97443
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-97443
- OSV: https://osv.dev/vulnerability/CVE-2026-97443

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-97443/
Summaries are generated and may contain mistakes; the official description above is the record.