CVE-2026-97609

In the Linux kernel, the following vulnerability has been resolved:

netfilter: cttimeout: prevent UAF during module unload

nf ct set timeout() protects the timeout hook dereference and policy lookup with rcu read lock(). cttimeout exit(), however, unregisters the per-net operations before it clears the hook.

This allows the following interleaving:

CPU 0 CPU 1 cttimeout exit() nf ct set timeout() unregister pernet subsys() rcu read lock() kfree(pernet) h = nf ct timeout hook h->timeout find get() nfct timeout pernet()

The hook still points to ctnl timeout find get() when CPU 1 looks up the already freed per-net timeout list. KASAN reported:

BUG: KASAN: slab-use-after-free in ctnl timeout find get Read of size 8 by task poc/90 Call Trace: ctnl timeout find get+0x271/0x2a0 [nfnetlink cttimeout] nf ct set timeout+0x7b/0x3c0 xt ct tg check+0x724/0xb20 xt check target+0x234/0xa90 do ipt set ctl+0x570/0x1270 Allocated by task 89: kmalloc noprof+0x16e/0x460 ops init+0x6d/0x420 register pernet operations+0x2f6/0x670 Freed by task 91: kfree+0x131/0x390 ops undo list+0x3d4/0x730 unregister pernet operations+0x232/0x490 unregister pernet subsys+0x1c/0x30 cttimeout exit+0x52/0x970 [nfnetlink cttimeout]

Clear the hook and wait for existing readers before unregistering the per-net operations. This blocks new policy lookups and ensures readers that observed the hook finish before the per-net storage is freed.