# CVE-2022-48976: netfilter: flowtable_offload: fix using __this_cpu_add in preemptible

> A bug in the Linux kernel netfilter flowtable offload module causes a kernel warning and potential instability when using per-CPU counters in preemptible contexts.

- **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 Oct 2024
- **Updated:** 23 May 2026
- **Also known as:** AZL-51327, DEBIAN-CVE-2022-48976, GHSA-3v5r-242w-7766, ROOT-OS-UBUNTU-2204-CVE-2022-48976, UBUNTU-CVE-2022-48976

## What is CVE-2022-48976?

CVE-2022-48976 is a medium-severity denial of service 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:

netfilter: flowtable_offload: fix using __this_cpu_add in preemptible

flow_offload_queue_work() can be called in workqueue without
bh disabled, like the call trace showed in my act_ct testing,
calling NF_FLOW_TABLE_STAT_INC() there would cause a call
trace:

  BUG: using __this_cpu_add() in preemptible [00000000] code: kworker/u4:0/138560
  caller is flow_offload_queue_work+0xec/0x1b0 [nf_flow_table]
  Workqueue: act_ct_workqueue tcf_ct_flow_table_cleanup_work [act_ct]
  Call Trace:
   <TASK>
   dump_stack_lvl+0x33/0x46
   check_preemption_disabled+0xc3/0xf0
   flow_offload_queue_work+0xec/0x1b0 [nf_flow_table]
   nf_flow_table_iterate+0x138/0x170 [nf_flow_table]
   nf_flow_table_free+0x140/0x1a0 [nf_flow_table]
   tcf_ct_flow_table_cleanup_work+0x2f/0x2b0 [act_ct]
   process_one_work+0x6a3/0x1030
   worker_thread+0x8a/0xdf0

This patch fixes it by using NF_FLOW_TABLE_STAT_INC_ATOMIC()
instead in flow_offload_queue_work().

Note that for FLOW_CLS_REPLACE branch in flow_offload_queue_work(),
it may not be called in preemptible path, but it's good to use
NF_FLOW_TABLE_STAT_INC_ATOMIC() for all cases in
flow_offload_queue_work().

## Which versions are affected by CVE-2022-48976?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2022-48976?

Apply the vendor's patch.

## Is CVE-2022-48976 being exploited?

There is no known exploitation of CVE-2022-48976 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-2022-48976 and fix it if it is affected.

What it is: CVE-2022-48976 is a medium-severity denial of service 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-2022-48976 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-2022-48976/ (Markdown: https://insights.sbomify.com/CVE-2022-48976/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2022-48976
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2022-48976
- OSV: https://osv.dev/vulnerability/CVE-2022-48976

---
From sbomify Insights: https://insights.sbomify.com/CVE-2022-48976/
Summaries are generated and may contain mistakes; the official description above is the record.