CVE-2025-40347: 
Linux Kernel vulnerability analysis and mitigation

CVE-2025-40347 is a deadlock vulnerability in the Linux kernel's ENETC (NXP Ethernet Controller) network driver, specifically in the enetc_mdio_lock read-write lock handling. The flaw affects the LS1028A platform running an RT (real-time) kernel and is triggered by recursive acquisition of the enetc_mdio_lock read lock within the enetc_poll path, causing RCU stalls and thread hangs. It was published on December 16, 2025, and affects Linux kernel versions from commit 6d36ecdbc441 up to the patched stable releases (6.6.115, 6.12.56, 6.17.6, and 6.18). No CVSS score has been assigned at this time (Feedly, EUVD).

The root cause is a deadlock condition (CWE-667: Improper Locking) arising from recursive acquisition of the enetc_mdio_lock read lock in the Linux kernel's ENETC driver. Under the enetc_poll path, after the read lock is acquired, a higher-priority writer attempts to acquire the same lock and is preempted; subsequent readers in the same call chain (e.g., via napi_gro_receive → enetc_start_xmit → enetc_lock_mdio) cannot re-acquire the read lock because the writer is already waiting, resulting in a thread hang. The fix adjusts enetc_lock_mdio to detect and prevent recursive lock acquisition, resolving the deadlock (Feedly, EUVD).

Successful triggering of this vulnerability causes a kernel deadlock and RCU stalls on affected LS1028A systems running an RT kernel, resulting in a denial of service (system hang or unresponsive network subsystem). The impact is limited to availability — there is no evidence of confidentiality or integrity compromise. Systems relying on the ENETC driver for network connectivity would experience complete loss of network functionality until the deadlock is resolved, typically requiring a reboot (Feedly).

The Linux kernel maintainers have released patches across multiple stable branches. The fix is included in kernel versions 6.6.115, 6.12.56, 6.17.6, and 6.18. Users should update to one of these patched versions. The fix modifies enetc_lock_mdio to prevent recursive lock acquisition, eliminating the deadlock condition. Patch commits are available at the kernel stable repository (EUVD, Feedly).