# CVE-2026-64512: ACPI: CPPC: Suppress UBSAN warning caused by field misuse

> A local attacker can trigger a kernel crash via an integer overflow in ACPI CPPC handling, affecting Linux kernel stability.

- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 25 Jul 2026
- **Updated:** 17 Aug 2026
- **Also known as:** AZL-93852, BELL-CVE-2026-64512, DEBIAN-CVE-2026-64512, GHSA-gqx5-8446-4x25, ROOT-OS-UBUNTU-2204-CVE-2026-64512, UBUNTU-CVE-2026-64512

## What is CVE-2026-64512?

CVE-2026-64512 is a vulnerability in Linux, published on 25 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:

ACPI: CPPC: Suppress UBSAN warning caused by field misuse

The definition of reg->access_width changes depending on the
reg->space_id type.  Type ACPI_ADR_SPACE_PLATFORM_COMM uses
access_width to indicate the PCC region, which can result in a UBSAN
if the value is greater than 4.

For example:

 UBSAN: shift-out-of-bounds in drivers/acpi/cppc_acpi.c:1090:9
 shift exponent 32 is too large for 32-bit type 'int'
 CPU: 61 UID: 0 PID: 1220 Comm: (udev-worker) Not tainted 7.0.10-201.fc44.aarch64 #1 PREEMPT(lazy)
 Hardware name: To be filled by O.E.M.
 Call trace:
  ...(trimming)
  ubsan_epilogue+0x10/0x48
  __ubsan_handle_shift_out_of_bounds+0xdc/0x1e0
  cpc_write+0x4d0/0x670
  cppc_set_perf+0x18c/0x490
  cppc_cpufreq_cpu_init+0x1c8/0x380 [cppc_cpufreq]
  ... (trimming)

Lets fix this by validating the region type, as well as whether
access_width has a value. Then since we are returning bit_width
directly for ACPI_ADR_SPACE_PLATFORM_COMM, drop the code correcting
the size.

## Which versions are affected by CVE-2026-64512?


## How do I fix CVE-2026-64512?

Apply the vendor's patch.

## Is CVE-2026-64512 being exploited?

There is no known exploitation of CVE-2026-64512 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-64512 and fix it if it is affected.

What it is: CVE-2026-64512 is a vulnerability in Linux, published on 25 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-2026-64512 in the wild and no public exploit code.

Affected product: Linux. 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-2026-64512/ (Markdown: https://insights.sbomify.com/CVE-2026-64512/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-64512
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-64512
- OSV: https://osv.dev/vulnerability/CVE-2026-64512

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-64512/
Summaries are generated and may contain mistakes; the official description above is the record.