# CVE-2025-39680: i2c: rtl9300: Fix out-of-bounds bug in rtl9300_i2c_smbus_xfer

> A local attacker can trigger an out-of-bounds read in the RTL9300 I2C driver by providing a large block size, potentially causing a crash or leaking kernel memory.

- **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:** 5 Sep 2025
- **Updated:** 5 Aug 2026
- **Also known as:** BELL-CVE-2025-39680, DEBIAN-CVE-2025-39680, GHSA-qr79-p6wg-4p8q, UBUNTU-CVE-2025-39680

## What is CVE-2025-39680?

CVE-2025-39680 is a high-severity memory corruption vulnerability in Linux kernel, published on 5 Sep 2025. 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: rtl9300: Fix out-of-bounds bug in rtl9300_i2c_smbus_xfer

The data->block[0] variable comes from user. Without proper check,
the variable may be very large to cause an out-of-bounds bug.

Fix this bug by checking the value of data->block[0] first.

1. commit 39244cc75482 ("i2c: ismt: Fix an out-of-bounds bug in
   ismt_access()")
2. commit 92fbb6d1296f ("i2c: xgene-slimpro: Fix out-of-bounds bug in
   xgene_slimpro_i2c_xfer()")

Weakness: CWE-125 (Out-of-bounds Read)

## Which versions are affected by CVE-2025-39680?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2025-39680?

Apply the vendor's patch.

## Is CVE-2025-39680 being exploited?

There is no known exploitation of CVE-2025-39680 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-2025-39680 and fix it if it is affected.

What it is: CVE-2025-39680 is a high-severity memory corruption vulnerability in Linux kernel, published on 5 Sep 2025. 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-2025-39680 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-2025-39680/ (Markdown: https://insights.sbomify.com/CVE-2025-39680/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-39680
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-39680
- OSV: https://osv.dev/vulnerability/CVE-2025-39680

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-39680/
Summaries are generated and may contain mistakes; the official description above is the record.