# CVE-2024-49866: tracing/timerlat: Fix a race during cpuhp processing

> A race condition in the Linux kernel timerlat tracer can cause timer corruption and system warnings, potentially leading to denial of service.

- **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:** 21 Oct 2024
- **Updated:** 5 Aug 2026
- **Also known as:** AZL-53343, BELL-CVE-2024-49866, DEBIAN-CVE-2024-49866, GHSA-8r4r-8c3p-6r95, UBUNTU-CVE-2024-49866

## What is CVE-2024-49866?

CVE-2024-49866 is a high-severity vulnerability in Linux kernel, published on 21 Oct 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:

tracing/timerlat: Fix a race during cpuhp processing

There is another found exception that the "timerlat/1" thread was
scheduled on CPU0, and lead to timer corruption finally:

```
ODEBUG: init active (active state 0) object: ffff888237c2e108 object type: hrtimer hint: timerlat_irq+0x0/0x220
WARNING: CPU: 0 PID: 426 at lib/debugobjects.c:518 debug_print_object+0x7d/0xb0
Modules linked in:
CPU: 0 UID: 0 PID: 426 Comm: timerlat/1 Not tainted 6.11.0-rc7+ #45
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.13.0-1ubuntu1.1 04/01/2014
RIP: 0010:debug_print_object+0x7d/0xb0
...
Call Trace:
 <TASK>
 ? __warn+0x7c/0x110
 ? debug_print_object+0x7d/0xb0
 ? report_bug+0xf1/0x1d0
 ? prb_read_valid+0x17/0x20
 ? handle_bug+0x3f/0x70
 ? exc_invalid_op+0x13/0x60
 ? asm_exc_invalid_op+0x16/0x20
 ? debug_print_object+0x7d/0xb0
 ? debug_print_object+0x7d/0xb0
 ? __pfx_timerlat_irq+0x10/0x10
 __debug_object_init+0x110/0x150
 hrtimer_init+0x1d/0x60
 timerlat_main+0xab/0x2d0
 ? __pfx_timerlat_main+0x10/0x10
 kthread+0xb7/0xe0
 ? __pfx_kthread+0x10/0x10
 ret_from_fork+0x2d/0x40
 ? __pfx_kthread+0x10/0x10
 ret_from_fork_asm+0x1a/0x30
 </TASK>
```

After tracing the scheduling event, it was discovered that the migration
of the "timerlat/1" thread was performed during thread creation. Further
analysis confirmed that it is because the CPU online processing for
osnoise is implemented through workers, which is asynchronous with the
offline processing. When the worker was scheduled to create a thread, the
CPU may has already been removed from the cpu_online_mask during the offline
process, resulting in the inability to select the right CPU:

T1                       | T2
[CPUHP_ONLINE]           | cpu_device_down()
osnoise_hotplug_workfn() |
                         |     cpus_write_lock()
                         |     takedown_cpu(1)
                         |     cpus_write_unlock()
[CPUHP_OFFLINE]          |
    cpus_read_lock()     |
    start_kthread(1)     |
    cpus_read_unlock()   |

To fix this, skip online processing if the CPU is already offline.

Weakness: CWE-362 (Concurrent Execution using Shared Resource with Improper Synchronization)

## Which versions are affected by CVE-2024-49866?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2024-49866?

Apply the vendor's patch.

## Is CVE-2024-49866 being exploited?

There is no known exploitation of CVE-2024-49866 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-2024-49866 and fix it if it is affected.

What it is: CVE-2024-49866 is a high-severity vulnerability in Linux kernel, published on 21 Oct 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-2024-49866 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-2024-49866/ (Markdown: https://insights.sbomify.com/CVE-2024-49866/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2024-49866
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2024-49866
- OSV: https://osv.dev/vulnerability/CVE-2024-49866

---
From sbomify Insights: https://insights.sbomify.com/CVE-2024-49866/
Summaries are generated and may contain mistakes; the official description above is the record.