CVE-2026-23231netfilter: nf_tables: fix use-after-free in nf_tables_addchain()

Official description

In the Linux kernel, the following vulnerability has been resolved: netfilter: nf_tables: fix use-after-free in nf_tables_addchain() nf_tables_addchain() publishes the chain to table->chains via list_add_tail_rcu() (in nft_chain_add()) before registering hooks. If nf_tables_register_hook() then fails, the error path calls nft_chain_del() (list_del_rcu()) followed by nf_tables_chain_destroy() with no RCU grace period in between. This creates two use-after-free conditions: 1) Control-plane: nf_tables_dump_chains() traverses table->chains under rcu_read_lock(). A concurrent dump can still be walking the chain when the error path frees it. 2) Packet path: for NFPROTO_INET, nf_register_net_hook() briefly installs the IPv4 hook before IPv6 registration fails. Packets entering nft_do_chain() via the transient IPv4 hook can still be dereferencing chain->blob_gen_X when the error path frees the chain. Add synchronize_rcu() between nft_chain_del() and the chain destroy so that all RCU readers -- both dump threads and in-flight packet evaluation -- have finished before the chain is freed.

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/2a6586ecfa4ce1413daaafee250d2590e05f1a33
• https://git.kernel.org/stable/c/7017745068a9068904e1e7a1b170a5785647cc81
• https://git.kernel.org/stable/c/f3fe58ce37926a10115ede527d59b91bcc05400a
• https://git.kernel.org/stable/c/dbd0af8083dd201f07c49110b2ee93710abdff28
• https://git.kernel.org/stable/c/2f9a4ffeb763aec822f8ff3d1e82202d27d46d4b
• https://git.kernel.org/stable/c/71e99ee20fc3f662555118cf1159443250647533
• https://cert-portal.siemens.com/productcert/html/ssa-082556.html
• https://cert-portal.siemens.com/productcert/html/ssa-253495.html
• https://cert-portal.siemens.com/productcert/html/ssa-019113.html
• https://cert-portal.siemens.com/productcert/html/ssa-457936.html
• https://cert-portal.siemens.com/productcert/html/ssa-784472.html