GHSA-5M7P-36VH-9W8V
Vulnerability from github – Published: 2026-09-25 12:31 – Updated: 2026-10-30 15:33In 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.
{
"affected": [],
"aliases": [
"CVE-2026-97609"
],
"database_specific": {
"cwe_ids": [],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-09-25T11:17:14Z",
"severity": "HIGH"
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\nnetfilter: cttimeout: prevent UAF during module unload\n\nnf_ct_set_timeout() protects the timeout hook dereference and policy lookup\nwith rcu_read_lock(). cttimeout_exit(), however, unregisters the per-net\noperations before it clears the hook.\n\nThis allows the following interleaving:\n\n CPU 0 CPU 1\n cttimeout_exit() nf_ct_set_timeout()\n unregister_pernet_subsys() rcu_read_lock()\n kfree(pernet) h = nf_ct_timeout_hook\n h-\u003etimeout_find_get()\n nfct_timeout_pernet()\n\nThe hook still points to ctnl_timeout_find_get() when CPU 1 looks up the\nalready freed per-net timeout list. KASAN reported:\n\n BUG: KASAN: slab-use-after-free in ctnl_timeout_find_get\n Read of size 8 by task poc/90\n Call Trace:\n ctnl_timeout_find_get+0x271/0x2a0 [nfnetlink_cttimeout]\n nf_ct_set_timeout+0x7b/0x3c0\n xt_ct_tg_check+0x724/0xb20\n xt_check_target+0x234/0xa90\n do_ipt_set_ctl+0x570/0x1270\n Allocated by task 89:\n __kmalloc_noprof+0x16e/0x460\n ops_init+0x6d/0x420\n register_pernet_operations+0x2f6/0x670\n Freed by task 91:\n kfree+0x131/0x390\n ops_undo_list+0x3d4/0x730\n unregister_pernet_operations+0x232/0x490\n unregister_pernet_subsys+0x1c/0x30\n cttimeout_exit+0x52/0x970 [nfnetlink_cttimeout]\n\nClear the hook and wait for existing readers before unregistering the\nper-net operations. This blocks new policy lookups and ensures readers that\nobserved the hook finish before the per-net storage is freed.",
"id": "GHSA-5m7p-36vh-9w8v",
"modified": "2026-10-30T15:33:48Z",
"published": "2026-09-25T12:31:26Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-97609"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/1f69c570a73f2dedf75ea5166d47622d5fa958c1"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/73f353bec62509c776184e49a031c6145cec0d05"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/763787e9d43982d1082b59caeabd317343b153ea"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/a7fdd86c386b7f7cc72a126389c2cdb55d035221"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/f664e06699829a31e95675a6864655a6c5f9904f"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/fec9b1de0d02de8dafa3cc344bcb91cf28660643"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H",
"type": "CVSS_V3"
}
]
}
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