CVE-2025-39871 dmaengine: idxd: Remove improper idxd_free
A use-after-free vulnerability in the Linux kernel idxd driver allows attackers to cause memory corruption or system crashes during module unload.
- 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-2025-39871?
CVE-2025-39871 is a high-severity use after free vulnerability in Linux kernel, published on 23 Sep 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:
dmaengine: idxd: Remove improper idxd_free
The call to idxd_free() introduces a duplicate put_device() leading to a reference count underflow: refcount_t: underflow; use-after-free. WARNING: CPU: 15 PID: 4428 at lib/refcount.c:28 refcount_warn_saturate+0xbe/0x110 ... Call Trace: <TASK> idxd_remove+0xe4/0x120 [idxd] pci_device_remove+0x3f/0xb0 device_release_driver_internal+0x197/0x200 driver_detach+0x48/0x90 bus_remove_driver+0x74/0xf0 pci_unregister_driver+0x2e/0xb0 idxd_exit_module+0x34/0x7a0 [idxd] __do_sys_delete_module.constprop.0+0x183/0x280 do_syscall_64+0x54/0xd70 entry_SYSCALL_64_after_hwframe+0x76/0x7e
The idxd_unregister_devices() which is invoked at the very beginning of idxd_remove(), already takes care of the necessary put_device() through the following call path: idxd_unregister_devices() -> device_unregister() -> put_device()
In addition, when CONFIG_DEBUG_KOBJECT_RELEASE is enabled, put_device() may trigger asynchronous cleanup via schedule_delayed_work(). If idxd_free() is called immediately after, it can result in a use-after-free.
Remove the improper idxd_free() to avoid both the refcount underflow and potential memory corruption during module unload.
Weakness: CWE-416
Which versions are affected by CVE-2025-39871?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2025-39871?
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-2025-39871 being exploited?
There is no known exploitation of CVE-2025-39871 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as BELL-CVE-2025-39871, DEBIAN-CVE-2025-39871, GHSA-frjr-mhww-g3pw, ROOT-OS-DEBIAN-12-CVE-2025-39871, UBUNTU-CVE-2025-39871.