# CVE-2026-89721: phy: rockchip-samsung-dcphy: fix out-of-range max_register

> A local attacker with debugfs access can trigger an out-of-bounds read in the Rockchip Samsung DCPHY driver, causing a kernel oops and subsequent deadlock.

- **Severity:** Not scored
- **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:** 11 Sep 2026
- **Updated:** 19 Oct 2026
- **Also known as:** BELL-CVE-2026-89721, DEBIAN-CVE-2026-89721, GHSA-jrrm-mv6f-g3m6, UBUNTU-CVE-2026-89721

## What is CVE-2026-89721?

CVE-2026-89721 is a memory corruption vulnerability in Linux, published on 11 Sep 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:

phy: rockchip-samsung-dcphy: fix out-of-range max_register

The PHY register block is 64KB, so with a register stride of 4 the
last accessible register sits at offset 0xfffc. max_register names
0x10000, one register past the end of the mapping: dumping the
registers through the regmap debugfs interface reads beyond the
ioremapped region and oopses on the unmapped page. The oops fires
with the regmap lock held, so later PHY operations deadlock.

## Which versions are affected by CVE-2026-89721?


## How do I fix CVE-2026-89721?

Apply the vendor's patch.

## Is CVE-2026-89721 being exploited?

There is no known exploitation of CVE-2026-89721 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-89721 and fix it if it is affected.

What it is: CVE-2026-89721 is a memory corruption vulnerability in Linux, published on 11 Sep 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-2026-89721 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-2026-89721/ (Markdown: https://insights.sbomify.com/CVE-2026-89721/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-89721
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-89721
- OSV: https://osv.dev/vulnerability/CVE-2026-89721

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-89721/
Summaries are generated and may contain mistakes; the official description above is the record.