CVE-2025-22126 md: fix mddev uaf while iterating all_mddevs list
A use-after-free vulnerability in the Linux kernel's md driver allows local attackers to potentially execute code or escalate privileges via a race condition.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2025-22126?
CVE-2025-22126 is a high-severity use after free vulnerability in Linux kernel, published on 16 Apr 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:
md: fix mddev uaf while iterating all_mddevs list
While iterating all_mddevs list from md_notify_reboot() and md_exit(), list_for_each_entry_safe is used, and this can race with deletint the next mddev, causing UAF:
t1: spin_lock //list_for_each_entry_safe(mddev, n, ...) mddev_get(mddev1) // assume mddev2 is the next entry spin_unlock t2: //remove mddev2 ... mddev_free spin_lock list_del spin_unlock kfree(mddev2) mddev_put(mddev1) spin_lock //continue dereference mddev2->all_mddevs
The old helper for_each_mddev() actually grab the reference of mddev2 while holding the lock, to prevent from being freed. This problem can be fixed the same way, however, the code will be complex.
Hence switch to use list_for_each_entry, in this case mddev_put() can free the mddev1 and it's not safe as well. Refer to md_seq_show(), also factor out a helper mddev_put_locked() to fix this problem.
Weakness: CWE-416
Which versions are affected by CVE-2025-22126?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2025-22126?
Apply the vendor's patch.
Upgrade to the fixed version. These bugs are found with fuzzing and sanitisers and avoided by memory-safe languages. More about Use after free.
Is CVE-2025-22126 being exploited?
There is no known exploitation of CVE-2025-22126 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as BELL-CVE-2025-22126, DEBIAN-CVE-2025-22126, GHSA-mg7c-mfqw-jg72, ROOT-OS-UBUNTU-2404-CVE-2025-22126, UBUNTU-CVE-2025-22126.