# CVE-2026-64086: hwmon: (pmbus/adm1266) include PEC byte in pmbus_block_xfer read buffer

> A buffer overflow in the Linux kernel adm1266 PMBus driver allows attackers to write one byte past the end of a buffer, potentially leading to code execution or system crashes.

- **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:** 19 Jul 2026
- **Updated:** 5 Aug 2026
- **Also known as:** BELL-CVE-2026-64086, DEBIAN-CVE-2026-64086, GHSA-f42m-8rh7-xp4f, UBUNTU-CVE-2026-64086

## What is CVE-2026-64086?

CVE-2026-64086 is a high-severity memory corruption vulnerability in Linux kernel, published on 19 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:

hwmon: (pmbus/adm1266) include PEC byte in pmbus_block_xfer read buffer

adm1266_pmbus_block_xfer() sets up the read transaction with

	.buf = data->read_buf,
	.len = ADM1266_PMBUS_BLOCK_MAX + 2,

but read_buf in struct adm1266_data is declared as

	u8 read_buf[ADM1266_PMBUS_BLOCK_MAX + 1];

For a max-length block response (length byte = 255 + up to 1 PEC
byte), the i2c controller is told to write 257 bytes into a 256-byte
buffer, putting one byte past the end of read_buf.  The same response
also makes the subsequent PEC compare

	if (crc != msgs[1].buf[msgs[1].buf[0] + 1])

read a byte beyond the array.

Bump the read_buf declaration to ADM1266_PMBUS_BLOCK_MAX + 2 so the
buffer can hold the length byte, up to 255 payload bytes, and the PEC
byte the i2c_msg length already accounts for.

## Which versions are affected by CVE-2026-64086?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2026-64086?

Apply the vendor's patch.

## Is CVE-2026-64086 being exploited?

There is no known exploitation of CVE-2026-64086 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-2026-64086 and fix it if it is affected.

What it is: CVE-2026-64086 is a high-severity memory corruption vulnerability in Linux kernel, published on 19 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-2026-64086 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-2026-64086/ (Markdown: https://insights.sbomify.com/CVE-2026-64086/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-64086
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-64086
- OSV: https://osv.dev/vulnerability/CVE-2026-64086

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-64086/
Summaries are generated and may contain mistakes; the official description above is the record.