The Linux kernel netfilter x_tables subsystem had a race condition where arp/ip(6)t_register_table() added a table to the per-network namespace list before allocating the per-netns hook operations. This created a window where the table was visible with a NULL ops pointer. Concurrent network namespace exit could trigger a pre_exit callback that dereferenced this NULL pointer in nf_unregister_net_hooks(), causing a general protection fault. The fix moves ops allocation into the xtables core to ensure the table is never listed without valid ops and synchronizes RCU callbacks if an error occurs during hook registration.

A NULL pointer dereference in the kernel can cause a general protection fault, leading to a kernel crash (panic) and denial of service for the affected system. There is no indication of privilege escalation or code execution. No known exploits are reported in the wild.

The vulnerability has been resolved by a kernel patch that changes the allocation order and adds synchronization to prevent NULL dereferences. Users should apply the official Linux kernel updates that include this fix. Patch status is not explicitly confirmed in the provided data; check the vendor or kernel mailing list advisories for the exact fixed versions and apply updates accordingly.