# CVE-2026-72142: i2c: imx: fix locked bus on SMBus block-read of 0 (atomic)

> A flaw in the Linux kernel i2c imx driver causes a bus lockup during specific SMBus block reads, requiring a power cycle to recover.

- **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:** 15 Aug 2026
- **Updated:** 23 Aug 2026
- **Also known as:** BELL-CVE-2026-72142, DEBIAN-CVE-2026-72142, GHSA-63x6-874m-qjjg, UBUNTU-CVE-2026-72142

## What is CVE-2026-72142?

CVE-2026-72142 is a denial of service vulnerability in Linux, published on 15 Aug 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:

i2c: imx: fix locked bus on SMBus block-read of 0 (atomic)

SMBus 3.1 6.5.7 allows a Block Read byte count of 0, but the atomic
(polling) path rejects it as -EPROTO. Worse, it returns without a
NACK+STOP: the next receive cycle has already started, so the target
keeps holding SDA and the bus stays stuck until a power cycle for
this i2c controller.

Reading I2DR to obtain the count likewise arms the next byte on the
count > I2C_SMBUS_BLOCK_MAX path, which also returned -EPROTO directly
and left the bus held.

Handle both: NACK the in-flight dummy byte (TXAK) and extend msgs->len so
the existing last-byte handling emits STOP; the dummy byte is discarded.
A count of 0 is a valid empty block read; a count above
I2C_SMBUS_BLOCK_MAX is still reported as -EPROTO, but only after the bus
has been released.

The interrupt-driven path has the same flaw from a later commit and is
fixed separately, as it carries a different Fixes: tag and stable range.

## Which versions are affected by CVE-2026-72142?


## How do I fix CVE-2026-72142?

Apply the vendor's patch.

## Is CVE-2026-72142 being exploited?

There is no known exploitation of CVE-2026-72142 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-72142 and fix it if it is affected.

What it is: CVE-2026-72142 is a denial of service vulnerability in Linux, published on 15 Aug 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-2026-72142 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-2026-72142/ (Markdown: https://insights.sbomify.com/CVE-2026-72142/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-72142
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-72142
- OSV: https://osv.dev/vulnerability/CVE-2026-72142

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-72142/
Summaries are generated and may contain mistakes; the official description above is the record.