# CVE-2026-23168: flex_proportions: make fprop_new_period() hardirq safe

> A race condition in the Linux kernel's flexible proportions code can cause an infinite loop and system hang when specific block device configurations are used.

- **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:** 14 Feb 2026
- **Updated:** 11 May 2026
- **Also known as:** AZL-77733, BELL-CVE-2026-23168, DEBIAN-CVE-2026-23168, GHSA-7xmm-c998-f7c9, ROOT-OS-UBUNTU-2404-CVE-2026-23168, UBUNTU-CVE-2026-23168

## What is CVE-2026-23168?

CVE-2026-23168 is a medium-severity vulnerability in Linux kernel, published on 14 Feb 2026. 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:

flex_proportions: make fprop_new_period() hardirq safe

Bernd has reported a lockdep splat from flexible proportions code that is
essentially complaining about the following race:

<timer fires>
run_timer_softirq - we are in softirq context
  call_timer_fn
    writeout_period
      fprop_new_period
        write_seqcount_begin(&p->sequence);

        <hardirq is raised>
        ...
        blk_mq_end_request()
	  blk_update_request()
	    ext4_end_bio()
	      folio_end_writeback()
		__wb_writeout_add()
		  __fprop_add_percpu_max()
		    if (unlikely(max_frac < FPROP_FRAC_BASE)) {
		      fprop_fraction_percpu()
			seq = read_seqcount_begin(&p->sequence);
			  - sees odd sequence so loops indefinitely

Note that a deadlock like this is only possible if the bdi has configured
maximum fraction of writeout throughput which is very rare in general but
frequent for example for FUSE bdis.  To fix this problem we have to make
sure write section of the sequence counter is irqsafe.

## Which versions are affected by CVE-2026-23168?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2026-23168?

Apply the vendor's patch.

## Is CVE-2026-23168 being exploited?

There is no known exploitation of CVE-2026-23168 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-2026-23168 and fix it if it is affected.

What it is: CVE-2026-23168 is a medium-severity vulnerability in Linux kernel, published on 14 Feb 2026. 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-2026-23168 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-2026-23168/ (Markdown: https://insights.sbomify.com/CVE-2026-23168/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-23168
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-23168
- OSV: https://osv.dev/vulnerability/CVE-2026-23168

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-23168/
Summaries are generated and may contain mistakes; the official description above is the record.