# CVE-2026-89725: media: cec: stm32: prevent out-of-bounds write on RX overflow

> A remote CEC peer can trigger an out-of-bounds write in the STM32 CEC driver, potentially leading to kernel memory corruption and privilege escalation.

- **Severity:** High 8.8 (`CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H`)
- **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:** 11 Sep 2026
- **Updated:** 19 Oct 2026
- **Also known as:** BELL-CVE-2026-89725, DEBIAN-CVE-2026-89725, GHSA-946x-47hf-5c7p, UBUNTU-CVE-2026-89725

## What is CVE-2026-89725?

CVE-2026-89725 is a high-severity 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:

media: cec: stm32: prevent out-of-bounds write on RX overflow

stm32_rx_done() appends each received CEC byte to rx_msg.msg[] using
rx_msg.len as the write index, incrementing it on every RXBR
(receive-byte-ready) interrupt without checking it against the buffer
size:

	cec->rx_msg.msg[cec->rx_msg.len++] = val & 0xFF;

rx_msg.msg[] is a fixed CEC_MAX_MSG_SIZE (16) byte array in struct
cec_msg, and rx_msg.len is only reset on RXACKE/RXOVR or after a
completed message (RXEND). The number of bytes received before RXEND is
decided by the remote CEC device (it sets EOM), not by the driver. A
peer that keeps sending bytes without ending the message drives RXBR
repeatedly, pushing rx_msg.len past 16 and writing peer-controlled bytes
out of bounds into the surrounding memory. This is reachable in normal
operation once the driver has probed and receiving is enabled, from the
IRQ thread, without any local privilege.

The length check in the CEC core runs on the consumer side, after the
byte has been stored, so it does not prevent the overflow. Bound the
index in the driver before the store, as the other platform CEC drivers
already do (e.g. tegra_cec), dropping the excess bytes of an overlong
frame.

Found by static analysis tool CodeQL.

## Which versions are affected by CVE-2026-89725?


## How do I fix CVE-2026-89725?

Apply the vendor's patch.

## Is CVE-2026-89725 being exploited?

There is no known exploitation of CVE-2026-89725 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-89725 and fix it if it is affected.

What it is: CVE-2026-89725 is a high-severity 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-2026-89725 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-2026-89725/ (Markdown: https://insights.sbomify.com/CVE-2026-89725/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-89725
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-89725
- OSV: https://osv.dev/vulnerability/CVE-2026-89725

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-89725/
Summaries are generated and may contain mistakes; the official description above is the record.