# CVE-2024-57849: s390/cpum_sf: Handle CPU hotplug remove during sampling

> A use-after-free vulnerability in the Linux kernel s390 CPUMF sampling driver allows attackers to potentially execute code or escalate privileges during CPU hotplug events.

- **Severity:** High 7.8 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/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:** 11 Jan 2025
- **Updated:** 15 Oct 2026
- **Also known as:** BELL-CVE-2024-57849, DEBIAN-CVE-2024-57849, GHSA-q4cg-m7j8-ggr6, ROOT-OS-DEBIAN-11-CVE-2024-57849, UBUNTU-CVE-2024-57849

## What is CVE-2024-57849?

CVE-2024-57849 is a high-severity use after free vulnerability in Linux kernel, published on 11 Jan 2025. 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:

s390/cpum_sf: Handle CPU hotplug remove during sampling

CPU hotplug remove handling triggers the following function
call sequence:

   CPUHP_AP_PERF_S390_SF_ONLINE  --> s390_pmu_sf_offline_cpu()
   ...
   CPUHP_AP_PERF_ONLINE          --> perf_event_exit_cpu()

The s390 CPUMF sampling CPU hotplug handler invokes:

 s390_pmu_sf_offline_cpu()
 +-->  cpusf_pmu_setup()
       +--> setup_pmc_cpu()
            +--> deallocate_buffers()

This function de-allocates all sampling data buffers (SDBs) allocated
for that CPU at event initialization. It also clears the
PMU_F_RESERVED bit. The CPU is gone and can not be sampled.

With the event still being active on the removed CPU, the CPU event
hotplug support in kernel performance subsystem triggers the
following function calls on the removed CPU:

  perf_event_exit_cpu()
  +--> perf_event_exit_cpu_context()
       +--> __perf_event_exit_context()
	    +--> __perf_remove_from_context()
	         +--> event_sched_out()
	              +--> cpumsf_pmu_del()
	                   +--> cpumsf_pmu_stop()
                                +--> hw_perf_event_update()

to stop and remove the event. During removal of the event, the
sampling device driver tries to read out the remaining samples from
the sample data buffers (SDBs). But they have already been freed
(and may have been re-assigned). This may lead to a use after free
situation in which case the samples are most likely invalid. In the
best case the memory has not been reassigned and still contains
valid data.

Remedy this situation and check if the CPU is still in reserved
state (bit PMU_F_RESERVED set). In this case the SDBs have not been
released an contain valid data. This is always the case when
the event is removed (and no CPU hotplug off occured).
If the PMU_F_RESERVED bit is not set, the SDB buffers are gone.

Weakness: CWE-416 (Use After Free)

## Which versions are affected by CVE-2024-57849?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2024-57849?

Apply the vendor's patch.

## Is CVE-2024-57849 being exploited?

There is no known exploitation of CVE-2024-57849 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-2024-57849 and fix it if it is affected.

What it is: CVE-2024-57849 is a high-severity use after free vulnerability in Linux kernel, published on 11 Jan 2025. 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-2024-57849 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-2024-57849/ (Markdown: https://insights.sbomify.com/CVE-2024-57849/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2024-57849
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2024-57849
- OSV: https://osv.dev/vulnerability/CVE-2024-57849

---
From sbomify Insights: https://insights.sbomify.com/CVE-2024-57849/
Summaries are generated and may contain mistakes; the official description above is the record.