CVE-2026-97609
HighCVSS 7.0Summary
A use-after-free vulnerability was found in the Linux kernel's netfilter cttimeout module during module unload. nf_ct_set_timeout() protects the timeout hook and policy lookup with rcu_read_lock(), but cttimeout_exit() unregisters per-net operations before clearing the hook, allowing access to freed memory. KASAN reported slab-use-after-free in ctnl_timeout_find_get.
Risk Assessment
An attacker could exploit this vulnerability to access freed kernel memory, potentially leading to privilege escalation, information disclosure, or system crash (DoS). The issue occurs during module unload of nfnetlink_cttimeout and may be triggered by a local user with appropriate privileges.
Recommendation
Immediately update the Linux kernel to a version containing the fix that clears the hook and waits for existing readers before unregistering per-net operations. Also monitor distribution security advisories and apply relevant patches.
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Original NVD description (English source)
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.
Vulnerability data from NVD (NIST) · CISA KEV · EPSS