CVE-2026-23458

In the Linux kernel, the following vulnerability has been resolved:<br /> <br /> netfilter: ctnetlink: fix use-after-free in ctnetlink_dump_exp_ct()<br /> <br /> ctnetlink_dump_exp_ct() stores a conntrack pointer in cb-&gt;data for the<br /> netlink dump callback ctnetlink_exp_ct_dump_table(), but drops the<br /> conntrack reference immediately after netlink_dump_start(). When the<br /> dump spans multiple rounds, the second recvmsg() triggers the dump<br /> callback which dereferences the now-freed conntrack via nfct_help(ct),<br /> leading to a use-after-free on ct-&gt;ext.<br /> <br /> The bug is that the netlink_dump_control has no .start or .done<br /> callbacks to manage the conntrack reference across dump rounds. Other<br /> dump functions in the same file (e.g. ctnetlink_get_conntrack) properly<br /> use .start/.done callbacks for this purpose.<br /> <br /> Fix this by adding .start and .done callbacks that hold and release the<br /> conntrack reference for the duration of the dump, and move the<br /> nfct_help() call after the cb-&gt;args[0] early-return check in the dump<br /> callback to avoid dereferencing ct-&gt;ext unnecessarily.<br /> <br /> BUG: KASAN: slab-use-after-free in ctnetlink_exp_ct_dump_table+0x4f/0x2e0<br /> Read of size 8 at addr ffff88810597ebf0 by task ctnetlink_poc/133<br /> <br /> CPU: 1 UID: 0 PID: 133 Comm: ctnetlink_poc Not tainted 7.0.0-rc2+ #3 PREEMPTLAZY<br /> Call Trace:<br /> <br /> ctnetlink_exp_ct_dump_table+0x4f/0x2e0<br /> netlink_dump+0x333/0x880<br /> netlink_recvmsg+0x3e2/0x4b0<br /> ? aa_sk_perm+0x184/0x450<br /> sock_recvmsg+0xde/0xf0<br /> <br /> Allocated by task 133:<br /> kmem_cache_alloc_noprof+0x134/0x440<br /> __nf_conntrack_alloc+0xa8/0x2b0<br /> ctnetlink_create_conntrack+0xa1/0x900<br /> ctnetlink_new_conntrack+0x3cf/0x7d0<br /> nfnetlink_rcv_msg+0x48e/0x510<br /> netlink_rcv_skb+0xc9/0x1f0<br /> nfnetlink_rcv+0xdb/0x220<br /> netlink_unicast+0x3ec/0x590<br /> netlink_sendmsg+0x397/0x690<br /> __sys_sendmsg+0xf4/0x180<br /> <br /> Freed by task 0:<br /> slab_free_after_rcu_debug+0xad/0x1e0<br /> rcu_core+0x5c3/0x9c0