cve 2026 31422

CVE-2026-31422 is a Linux kernel vulnerability in the net/sched/cls_flow module where flow_change() can dereference an unset block->q pointer when the filter is attached to a shared block, leading to a NULL pointer dereference and kernel crash. The flaw is triggered via tc_new_tfilter() and rtnetlink_rcv_msg(), with the crash reproduced at cls_flow.c:508. The fix adds a check for tcf_block_shared() to prevent the dereference. This tag covers discussions about the vulnerability, its reproduction, and the targeted patch for shared blocks in the Linux networking stack.