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Triggering it requires CAP_NET_ADMIN (including in a network namespace). I do not claim privilege escalation; the result we see is local DoS (KASAN slab UAF read). Summary ======= nf_tables_netdev_event() walks table->chains with list_for_each_entry_safe. On NETDEV_UNREGISTER it releases the netdev ingress base chain. A JUMP to an NFT_CHAIN_BINDING successor is deactivated (nft_chain_del + bound = false) and then nft_immediate_destroy() kfree's that successor. The walker's saved nr still points at the freed nft_chain, so the loop increment reads chain->list.next. The deactivate/destroy path: __nft_release_basechain_now() -> nft_rule_expr_deactivate(..., NFT_TRANS_RELEASE) -> nft_immediate_deactivate(): nft_chain_del(chain); chain->bound = false; -> nft_immediate_destroy(): nf_tables_chain_destroy() when !chain->bound list_for_each_entry_safe only protects deleting the current entry, not a sibling freed inside the loop body. Affected ======== - Confirmed on Linux 6.6.144, KASAN guest. - Files: net/netfilter/nft_chain_filter.c, net/netfilter/nft_immediate.c, net/netfilter/nf_tables_api.c - Config: CONFIG_NF_TABLES=y, CONFIG_NF_TABLES_NETDEV=y, CONFIG_BRIDGE=y (KASAN used for the report) - Source review of torvalds/linux master as of 2026-09-18: nft_immediate_deactivate() still unlinks binding chains on NFT_TRANS_RELEASE and nft_immediate_destroy() still destroys them when !chain->bound. __nft_release_basechain() is gone from nf_tables_api.c and the notifier only unregisters hooks on tip, so this PoC's live RTM_DELLINK trigger was not re-run on tip. Ruleset that triggers it ======================== table netdev t { chain in { type filter hook ingress device "br0" priority 0; jump j } chain j { flags binding; } } Create br0 in a network namespace, load the ruleset, then RTM_DELLINK br0 while the namespace is still alive (NETDEV_UNREGISTER). Netns teardown alone is too late: nft pernet exit wins that race. Crash excerpt (minimized PoC, Linux 6.6.144 KASAN) ================================================== BUG: KASAN: slab-use-after-free in nf_tables_netdev_event+0x699/0x7d0 Read of size 8 at addr ff11000009aefd20 by task repro/220 CPU: 0 PID: 220 Comm: repro Not tainted 6.6.144 #1 Call Trace: kasan_report nf_tables_netdev_event+0x699/0x7d0 notifier_call_chain unregister_netdevice_many_notify rtnl_dellink rtnetlink_rcv_msg Allocated by task 220: nf_tables_addchain nf_tables_newchain Freed by task 220: nf_tables_chain_destroy nft_immediate_destroy __nft_release_basechain_now __nft_release_basechain nf_tables_netdev_event+0x63a/0x7d0 The KASAN read is 8 bytes at offset 32 of a kmalloc-128 object (nft_chain.list). Reproducer ========== A self-contained C PoC (raw NETLINK_NETFILTER batch plus RTM_NEWLINK/ RTM_DELLINK, no nft binary) and a Docker/QEMU package are available on request. VM-only: the program triggers a guest KASAN UAF. Please do not run it on a host kernel. I am happy to test patches or send the reproducer. Thanks, Yu Junzhe FuzzAnything