CVE-2025-40347 net: enetc: fix the deadlock of enetc_mdio_lock
A deadlock in the enetc network driver causes system hangs on RT kernels, requiring a kernel patch to resolve.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2025-40347?
CVE-2025-40347 is a high-severity vulnerability in Linux, published on 16 Dec 2025. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
In the Linux kernel, the following vulnerability has been resolved:
net: enetc: fix the deadlock of enetc_mdio_lock
After applying the workaround for err050089, the LS1028A platform experiences RCU stalls on RT kernel. This issue is caused by the recursive acquisition of the read lock enetc_mdio_lock. Here list some of the call stacks identified under the enetc_poll path that may lead to a deadlock:
enetc_poll -> enetc_lock_mdio -> enetc_clean_rx_ring OR napi_complete_done -> napi_gro_receive -> enetc_start_xmit -> enetc_lock_mdio -> enetc_map_tx_buffs -> enetc_unlock_mdio -> enetc_unlock_mdio
After enetc_poll acquires the read lock, a higher-priority writer attempts to acquire the lock, causing preemption. The writer detects that a read lock is already held and is scheduled out. However, readers under enetc_poll cannot acquire the read lock again because a writer is already waiting, leading to a thread hang.
Currently, the deadlock is avoided by adjusting enetc_lock_mdio to prevent recursive lock acquisition.
Which versions are affected by CVE-2025-40347?
How do I fix CVE-2025-40347?
Apply the vendor's patch.
Is CVE-2025-40347 being exploited?
There is no known exploitation of CVE-2025-40347 in the wild and no public exploit code.
Sources
Also known as BELL-CVE-2025-40347, DEBIAN-CVE-2025-40347, GHSA-r9fm-4g8c-9hfh, ROOT-OS-DEBIAN-11-CVE-2025-40347, ROOT-OS-DEBIAN-12-CVE-2025-40347, ROOT-OS-UBUNTU-2204-CVE-2025-40347 and 2 more.