# CVE-2023-54139: tracing/user_events: Ensure write index cannot be negative

> A missing bounds check in Linux kernel user_events allows negative write indices, potentially leading to out-of-bounds memory access and privilege escalation.

- **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:** 24 Dec 2025
- **Updated:** 5 Aug 2026
- **Also known as:** BELL-CVE-2023-54139, DEBIAN-CVE-2023-54139, GHSA-8m37-c7gh-2jmr, UBUNTU-CVE-2023-54139

## What is CVE-2023-54139?

CVE-2023-54139 is a high-severity memory corruption vulnerability in Linux, published on 24 Dec 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:

tracing/user_events: Ensure write index cannot be negative

The write index indicates which event the data is for and accesses a
per-file array. The index is passed by user processes during write()
calls as the first 4 bytes. Ensure that it cannot be negative by
returning -EINVAL to prevent out of bounds accesses.

Update ftrace self-test to ensure this occurs properly.

## Which versions are affected by CVE-2023-54139?


## How do I fix CVE-2023-54139?

Apply the vendor's patch.

## Is CVE-2023-54139 being exploited?

There is no known exploitation of CVE-2023-54139 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2023-54139 and fix it if it is affected.

What it is: CVE-2023-54139 is a high-severity memory corruption vulnerability in Linux, published on 24 Dec 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-2023-54139 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-2023-54139/ (Markdown: https://insights.sbomify.com/CVE-2023-54139/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2023-54139
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2023-54139
- OSV: https://osv.dev/vulnerability/CVE-2023-54139

---
From sbomify Insights: https://insights.sbomify.com/CVE-2023-54139/
Summaries are generated and may contain mistakes; the official description above is the record.