# CVE-2024-43870: perf: Fix event leak upon exit

> A race condition in the Linux kernel perf subsystem causes event refcount leaks, potentially leading to memory exhaustion and denial of service.

- **Severity:** Medium 5.5 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H`)
- **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:** 21 Aug 2024
- **Updated:** 23 May 2026
- **Also known as:** BELL-CVE-2024-43870, DEBIAN-CVE-2024-43870, GHSA-24f8-f4wm-56gg, UBUNTU-CVE-2024-43870

## What is CVE-2024-43870?

CVE-2024-43870 is a medium-severity denial of service vulnerability in Linux kernel, published on 21 Aug 2024. 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: Fix event leak upon exit

When a task is scheduled out, pending sigtrap deliveries are deferred
to the target task upon resume to userspace via task_work.

However failures while adding an event's callback to the task_work
engine are ignored. And since the last call for events exit happen
after task work is eventually closed, there is a small window during
which pending sigtrap can be queued though ignored, leaking the event
refcount addition such as in the following scenario:

    TASK A
    -----

    do_exit()
       exit_task_work(tsk);

       <IRQ>
       perf_event_overflow()
          event->pending_sigtrap = pending_id;
          irq_work_queue(&event->pending_irq);
       </IRQ>
    =========> PREEMPTION: TASK A -> TASK B
       event_sched_out()
          event->pending_sigtrap = 0;
          atomic_long_inc_not_zero(&event->refcount)
          // FAILS: task work has exited
          task_work_add(&event->pending_task)
       [...]
       <IRQ WORK>
       perf_pending_irq()
          // early return: event->oncpu = -1
       </IRQ WORK>
       [...]
    =========> TASK B -> TASK A
       perf_event_exit_task(tsk)
          perf_event_exit_event()
             free_event()
                WARN(atomic_long_cmpxchg(&event->refcount, 1, 0) != 1)
                // leak event due to unexpected refcount == 2

As a result the event is never released while the task exits.

Fix this with appropriate task_work_add()'s error handling.

Weakness: CWE-401 (Missing Release of Memory after Effective Lifetime)

## Which versions are affected by CVE-2024-43870?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2024-43870?

Apply the vendor's patch.

## Is CVE-2024-43870 being exploited?

There is no known exploitation of CVE-2024-43870 in the wild and no public exploit code.

## Other vulnerabilities in Linux kernel

- [CVE-2026-53266](https://insights.sbomify.com/CVE-2026-53266/): Linux Kernel Out-of-Bounds Write (high 8.8, exploited in the wild)
- [CVE-2013-6282](https://insights.sbomify.com/CVE-2013-6282/): Linux Kernel Improper Input Validation (high 8.8, exploited in the wild)
- [CVE-2022-0185](https://insights.sbomify.com/CVE-2022-0185/): Linux Kernel Heap-Based Buffer Overflow (high 8.4, exploited in the wild)
- [CVE-2013-2094](https://insights.sbomify.com/CVE-2013-2094/): Linux Kernel Privilege Escalation (high 8.4, exploited in the wild)
- [CVE-2026-53362](https://insights.sbomify.com/CVE-2026-53362/): Linux Kernel Unspecified (high 7.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2024-43870 and fix it if it is affected.

What it is: CVE-2024-43870 is a medium-severity denial of service vulnerability in Linux kernel, published on 21 Aug 2024. 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-2024-43870 in the wild and no public exploit code.

Affected product: Linux kernel. 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-2024-43870/ (Markdown: https://insights.sbomify.com/CVE-2024-43870/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2024-43870
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2024-43870
- OSV: https://osv.dev/vulnerability/CVE-2024-43870

---
From sbomify Insights: https://insights.sbomify.com/CVE-2024-43870/
Summaries are generated and may contain mistakes; the official description above is the record.