# CVE-2026-74549: hwmon: (nct6775-core) Prevent access to unsupported weight registers

> A Linux kernel driver bug allows out-of-bounds reads leading to invalid hardware access, potentially causing system crashes or misconfiguration.

- **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:** 15 Aug 2026
- **Updated:** 19 Aug 2026
- **Also known as:** AZL-96561, BELL-CVE-2026-74549, DEBIAN-CVE-2026-74549, GHSA-8cf5-68w2-4vhx, UBUNTU-CVE-2026-74549

## What is CVE-2026-74549?

CVE-2026-74549 is a high-severity memory corruption 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:

hwmon: (nct6775-core) Prevent access to unsupported weight registers

Sashiko reports:

During initialization of the nct6116 chip, the driver sets data->pwm_num
to 5. However, it assigns several NCT6106 register arrays (such as
NCT6106_REG_WEIGHT_DUTY_STEP, NCT6106_REG_WEIGHT_TEMP_SEL, and
NCT6106_REG_WEIGHT_TEMP_*) to data->REG_PWM and data->REG_WEIGHT_TEMP.
These arrays only contain 3 elements.

In nct6775_update_pwm(), the driver iterates up to data->pwm_num. If
data->has_pwm has bits 3 or 4 set (which is structurally possible for
nct6116), the loop attempts to read elements at index 3 and 4 from these
3-element arrays. This results in a global out-of-bounds read, which can
be caught by KASAN.

Furthermore, the driver uses these garbage out-of-bounds values as
hardware register addresses for subsequent read and write operations. This
leads to invalid hardware register access, potentially causing hardware
misconfiguration or system crashes.

The underlying problem is that the chip does support up to five fan
control channels, but only the first three support weight control.
Fix the problem by extending the affected weight register arrays with
zeroed fields. The driver uses zeroed register addresses to determine
if a register is supported or not, and skips accesses for unsupported
registers.

## Which versions are affected by CVE-2026-74549?


## How do I fix CVE-2026-74549?

Apply the vendor's patch.

## Is CVE-2026-74549 being exploited?

There is no known exploitation of CVE-2026-74549 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-74549 and fix it if it is affected.

What it is: CVE-2026-74549 is a high-severity memory corruption 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-2026-74549 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-2026-74549/ (Markdown: https://insights.sbomify.com/CVE-2026-74549/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-74549
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-74549
- OSV: https://osv.dev/vulnerability/CVE-2026-74549

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-74549/
Summaries are generated and may contain mistakes; the official description above is the record.