# CVE-2026-64214: powerpc/time: Remove redundant preempt_disable|enable() calls from arch_irq_work_raise()

> A null pointer dereference in the Linux kernel powerpc module causes a system crash when handling machine check exceptions in real mode.

- **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:** 24 Jul 2026
- **Updated:** 24 Jul 2026
- **Also known as:** BELL-CVE-2026-64214, DEBIAN-CVE-2026-64214, GHSA-5qjx-3f5w-qj49, ROOT-OS-UBUNTU-2204-CVE-2026-64214, UBUNTU-CVE-2026-64214

## What is CVE-2026-64214?

CVE-2026-64214 is a medium-severity vulnerability in Linux kernel, published on 24 Jul 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:

powerpc/time: Remove redundant preempt_disable|enable() calls from arch_irq_work_raise()

A kernel panic is observed when handling machine check exceptions from
real mode.

  BUG: Unable to handle kernel data access on read at 0xc00000006be21300
  Oops: Kernel access of bad area, sig: 11 [#1]
  MSR:  8000000000001003 <SF,ME,RI,LE>  CR: 88222248  XER: 00000005
  CFAR: c00000000003ffc4 DAR: c00000006be21300 DSISR: 40000000 IRQMASK: 0
  NIP [c000000000029e40] arch_irq_work_raise+0x10/0x70
  LR [c00000000003ffc8] machine_check_queue_event+0xa8/0x150
  Call Trace:
  [c0000000179d3c70] [c00000000003ff64] machine_check_queue_event+0x44/0x150
  [c0000000179d3d30] [c0000000000084e0] machine_check_early_common+0x1f0/0x2c0

The crash occurs because arch_irq_work_raise() calls preempt_disable()
from machine check exception (MCE) handlers running in real mode. In
this context, accessing the preempt_count can fault, leading to the panic.

The preempt_disable()/preempt_enable() pair in arch_irq_work_raise()
was originally added by commit 0fe1ac48bef0 ("powerpc/perf_event: Fix
oops due to perf_event_do_pending call") to avoid races while raising
irq work from exception context.

Later, commit 471ba0e686cb ("irq_work: Do not raise an IPI when
queueing work on the local CPU") added preemption protection in
irq_work_queue() path, while commit 20b876918c06 ("irq_work: Use per
cpu atomics instead of regular atomics") added equivalent
protection in irq_work_queue_on() before reaching arch_irq_work_raise():

  irq_work_queue() / irq_work_queue_on()
    -> preempt_disable()
      -> __irq_work_queue_local()
        -> irq_work_raise()
          -> arch_irq_work_raise()

As a result, callers other than mce_irq_work_raise() already execute
with preemption disabled, making the additional
preempt_disable()/preempt_enable() pair in arch_irq_work_raise()
redundant.

The arch_irq_work_raise() function executes in NMI context when called
from MCE handler. Hence we will not be preempted or scheduled out since
we are in NMI context with MSR[EE]=0. Therefore, it is safe to remove
the preempt_disable()/preempt_enable() calls from here.

Remove it to avoid accessing preempt_count from real mode context.

[Maddy: Fixed the commit title]

Weakness: CWE-476 (NULL Pointer Dereference)

## Which versions are affected by CVE-2026-64214?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2026-64214?

Apply the vendor's patch.

## Is CVE-2026-64214 being exploited?

There is no known exploitation of CVE-2026-64214 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-2026-64214 and fix it if it is affected.

What it is: CVE-2026-64214 is a medium-severity vulnerability in Linux kernel, published on 24 Jul 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-2026-64214 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-2026-64214/ (Markdown: https://insights.sbomify.com/CVE-2026-64214/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-64214
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-64214
- OSV: https://osv.dev/vulnerability/CVE-2026-64214

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-64214/
Summaries are generated and may contain mistakes; the official description above is the record.