CVE-2026-64424 netpoll: fix a use-after-free on shutdown path
A use-after-free in the Linux kernel netpoll subsystem allows attackers to cause denial of service or potentially execute code during shutdown.
- 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-2026-64424?
CVE-2026-64424 is a high-severity use after free vulnerability in Linux kernel, published on 25 Jul 2026. 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:
netpoll: fix a use-after-free on shutdown path
There is a use-after-free error on netpoll, which is clearly detected by KASAN.
BUG: KASAN: slab-use-after-free in _raw_spin_lock_irqsave+0x3b/0x80 Read of size 1 at addr ... by task kworker/9:1 Workqueue: events queue_process Call Trace: skb_dequeue+0x1e/0xb0 queue_process+0x2c/0x600 process_scheduled_works+0x4b6/0x850 worker_thread+0x414/0x5a0 Allocated by task 242: __netpoll_setup+0x201/0x4a0 netpoll_setup+0x249/0x550 enabled_store+0x32f/0x380 Freed by task 0: kfree+0x1b7/0x540 rcu_core+0x3f8/0x7a0
The problem happens when there is a pending TX worker running in parallel with the cleanup path.
This is what happens on netpoll shutdown path:
1) __netpoll_cleanup() is called 2) set dev->npinfo to NULL 3) call_rcu() with rcu_cleanup_netpoll_info() 3.1) rcu_cleanup_netpoll_info() tries to cancel all workers with cancel_delayed_work(), but doesn't wait for the worker to finish 4) and kfree(npinfo);
Because 3.1) doesn't really cancel the work, as the comment says "we can't call cancel_delayed_work_sync here, as we are in softirq", the TX worker can run after 4).
Tl;DR: queue_process() is not an RCU reader, it reaches npinfo through the work item via container_of().
Use disable_delayed_work_sync() to ensure the worker is completely stopped and prevent any future re-arming attempts. Once npinfo is set to NULL, senders will bail out and not queue new work. The disable flag ensures any in-flight re-arming attempts also fail silently.
In the future, we can do the cleanup inline here without needing the npinfo->rcu rcu_head, but that is net-next material.
Weakness: CWE-416
Which versions are affected by CVE-2026-64424?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2026-64424?
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-2026-64424 being exploited?
There is no known exploitation of CVE-2026-64424 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as AZL-93455, BELL-CVE-2026-64424, DEBIAN-CVE-2026-64424, GHSA-4m75-5382-c595, ROOT-OS-UBUNTU-2204-CVE-2026-64424, UBUNTU-CVE-2026-64424.