CVE-2026-31421 net/sched: cls_fw: fix NULL pointer dereference on shared blocks

In the Linux kernel, the following vulnerability has been resolved: net/sched: clsfw: fix NULL pointer dereference on shared blocks The old-method path in fwclassify calls tcfblockq and dereferences q-handle. Shared blocks leave block-q NULL, causing a NULL deref when an empty clsfw filter is...