# CVE-2025-38621

## Summary

- **CVE ID:** CVE-2025-38621
- **Severity:** MEDIUM
- **CVSS Score:** 5.5 (CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H)
- **CWE:** N/A
- **Published:** Aug 22, 2025
- **Last Modified:** Sep 7, 2026

## Description

In the Linux kernel, the following vulnerability has been resolved:

md: make rdev_addable usable for rcu mode

Our testcase trigger panic:

BUG: kernel NULL pointer dereference, address: 00000000000000e0
...
Oops: Oops: 0000 [#1] SMP NOPTI
CPU: 2 UID: 0 PID: 85 Comm: kworker/2:1 Not tainted 6.16.0+ #94
PREEMPT(none)
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS
1.16.1-2.fc37 04/01/2014
Workqueue: md_misc md_start_sync
RIP: 0010:rdev_addable+0x4d/0xf0
...
Call Trace:
 <TASK>
 md_start_sync+0x329/0x480
 process_one_work+0x226/0x6d0
 worker_thread+0x19e/0x340
 kthread+0x10f/0x250
 ret_from_fork+0x14d/0x180
 ret_from_fork_asm+0x1a/0x30
 </TASK>
Modules linked in: raid10
CR2: 00000000000000e0
---[ end trace 0000000000000000 ]---
RIP: 0010:rdev_addable+0x4d/0xf0

md_spares_need_change in md_start_sync will call rdev_addable which
protected by rcu_read_lock/rcu_read_unlock. This rcu context will help
protect rdev won't be released, but rdev->mddev will be set to NULL
before we call synchronize_rcu in md_kick_rdev_from_array. Fix this by
using READ_ONCE and check does rdev->mddev still alive.

## Affected Products

- Linux — Linux (bc08041b32abe6c9824f78735bac22018eabfc06)
- Linux — Linux (6.7)
- Linux — Linux (0)
- Linux — Linux (6.16.1)
- Linux — Linux (6.17)
- Linux — Linux (6.12.109)

## References

- [CNA](https://git.kernel.org/stable/c/b5fbe940862339cdcc34dea7a057ad18d18fa137)
- [CNA](https://git.kernel.org/stable/c/13017b427118f4311471ee47df74872372ca8482)
- [CNA](https://git.kernel.org/stable/c/d713e105a6137d3f54f09d4d9e2273482057ca17)

## Exploitation Prediction (EPSS)

- **EPSS Score:** 0.16%
- **EPSS Percentile:** 5.4

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_Exported from OnDuty AI Vulnerability Intelligence on 2026-09-17._