# CVE-2025-39713: media: rainshadow-cec: fix TOCTOU race condition in rain_interrupt()

> A race condition in the rainshadow-cec driver allows buffer overflow, potentially leading to code execution or denial of service.

- **Severity:** Medium 4.7 (`CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/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:** 12 May 2026
- **Also known as:** BELL-CVE-2025-39713, DEBIAN-CVE-2025-39713, GHSA-pf4v-7q2j-5rw9, ROOT-OS-DEBIAN-11-CVE-2025-39713, ROOT-OS-DEBIAN-12-CVE-2025-39713, ROOT-OS-DEBIAN-13-CVE-2025-39713, ROOT-OS-UBUNTU-2204-CVE-2025-39713, ROOT-OS-UBUNTU-2404-CVE-2025-39713, UBUNTU-CVE-2025-39713

## What is CVE-2025-39713?

CVE-2025-39713 is a medium-severity vulnerability in Debian Debian Linux, 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:

media: rainshadow-cec: fix TOCTOU race condition in rain_interrupt()

In the interrupt handler rain_interrupt(), the buffer full check on
rain->buf_len is performed before acquiring rain->buf_lock. This
creates a Time-of-Check to Time-of-Use (TOCTOU) race condition, as
rain->buf_len is concurrently accessed and modified in the work
handler rain_irq_work_handler() under the same lock.

Multiple interrupt invocations can race, with each reading buf_len
before it becomes full and then proceeding. This can lead to both
interrupts attempting to write to the buffer, incrementing buf_len
beyond its capacity (DATA_SIZE) and causing a buffer overflow.

Fix this bug by moving the spin_lock() to before the buffer full
check. This ensures that the check and the subsequent buffer modification
are performed atomically, preventing the race condition. An corresponding
spin_unlock() is added to the overflow path to correctly release the
lock.

This possible bug was found by an experimental static analysis tool
developed by our team.

Weakness: CWE-367 (Time-of-check Time-of-use (TOCTOU) Race Condition)

## Which versions are affected by CVE-2025-39713?

It affects 2 products.


Products: Debian Debian Linux, Linux kernel.

## How do I fix CVE-2025-39713?

Apply the vendor's patch.

## Is CVE-2025-39713 being exploited?

There is no known exploitation of CVE-2025-39713 in the wild and no public exploit code.

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## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2025-39713 and fix it if it is affected.

What it is: CVE-2025-39713 is a medium-severity vulnerability in Debian Debian Linux, 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-2025-39713 in the wild and no public exploit code.

Affected product: Debian Debian 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-2025-39713/ (Markdown: https://insights.sbomify.com/CVE-2025-39713/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-39713
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-39713
- OSV: https://osv.dev/vulnerability/CVE-2025-39713

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-39713/
Summaries are generated and may contain mistakes; the official description above is the record.