# CVE-2025-71197: w1: therm: Fix off-by-one buffer overflow in alarms_store

> An off-by-one buffer overflow in the Linux kernel w1 therm driver allows local attackers to potentially execute code or escalate privileges.

- **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:** 4 Feb 2026
- **Updated:** 15 Oct 2026
- **Also known as:** AZL-77211, BELL-CVE-2025-71197, DEBIAN-CVE-2025-71197, GHSA-4c4g-c6q5-6cpq, ROOT-OS-UBUNTU-2204-CVE-2025-71197, ROOT-OS-UBUNTU-2404-CVE-2025-71197, UBUNTU-CVE-2025-71197

## What is CVE-2025-71197?

CVE-2025-71197 is a memory corruption vulnerability in Linux, published on 4 Feb 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:

w1: therm: Fix off-by-one buffer overflow in alarms_store

The sysfs buffer passed to alarms_store() is allocated with 'size + 1'
bytes and a NUL terminator is appended. However, the 'size' argument
does not account for this extra byte. The original code then allocated
'size' bytes and used strcpy() to copy 'buf', which always writes one
byte past the allocated buffer since strcpy() copies until the NUL
terminator at index 'size'.

Fix this by parsing the 'buf' parameter directly using simple_strtoll()
without allocating any intermediate memory or string copying. This
removes the overflow while simplifying the code.

## Which versions are affected by CVE-2025-71197?


## How do I fix CVE-2025-71197?

Apply the vendor's patch.

## Is CVE-2025-71197 being exploited?

There is no known exploitation of CVE-2025-71197 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2025-71197 and fix it if it is affected.

What it is: CVE-2025-71197 is a memory corruption vulnerability in Linux, published on 4 Feb 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-2025-71197 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-2025-71197/ (Markdown: https://insights.sbomify.com/CVE-2025-71197/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-71197
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-71197
- OSV: https://osv.dev/vulnerability/CVE-2025-71197

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-71197/
Summaries are generated and may contain mistakes; the official description above is the record.