# CVE-2023-54039: can: j1939: j1939_tp_tx_dat_new(): fix out-of-bounds memory access

> An out-of-bounds memory access in the Linux kernel J1939 CAN protocol allows attackers to cause denial of service or potentially execute code.

- **Severity:** Not scored
- **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:** 24 Dec 2025
- **Updated:** 11 May 2026
- **Also known as:** BELL-CVE-2023-54039, DEBIAN-CVE-2023-54039, GHSA-3q37-wmq7-mf4x, UBUNTU-CVE-2023-54039

## What is CVE-2023-54039?

CVE-2023-54039 is a 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:

can: j1939: j1939_tp_tx_dat_new(): fix out-of-bounds memory access

In the j1939_tp_tx_dat_new() function, an out-of-bounds memory access
could occur during the memcpy() operation if the size of skb->cb is
larger than the size of struct j1939_sk_buff_cb. This is because the
memcpy() operation uses the size of skb->cb, leading to a read beyond
the struct j1939_sk_buff_cb.

Updated the memcpy() operation to use the size of struct
j1939_sk_buff_cb instead of the size of skb->cb. This ensures that the
memcpy() operation only reads the memory within the bounds of struct
j1939_sk_buff_cb, preventing out-of-bounds memory access.

Additionally, add a BUILD_BUG_ON() to check that the size of skb->cb
is greater than or equal to the size of struct j1939_sk_buff_cb. This
ensures that the skb->cb buffer is large enough to hold the
j1939_sk_buff_cb structure.

[mkl: rephrase commit message]

## Which versions are affected by CVE-2023-54039?


## How do I fix CVE-2023-54039?

Apply the vendor's patch.

## Is CVE-2023-54039 being exploited?

There is no known exploitation of CVE-2023-54039 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2023-54039 and fix it if it is affected.

What it is: CVE-2023-54039 is a 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-2023-54039 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-2023-54039/ (Markdown: https://insights.sbomify.com/CVE-2023-54039/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2023-54039
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2023-54039
- OSV: https://osv.dev/vulnerability/CVE-2023-54039

---
From sbomify Insights: https://insights.sbomify.com/CVE-2023-54039/
Summaries are generated and may contain mistakes; the official description above is the record.