GHSA-PQG4-X7W2-6F65
Vulnerability from github – Published: 2026-04-03 18:31 – Updated: 2026-10-15 03:35In the Linux kernel, the following vulnerability has been resolved:
netfilter: ctnetlink: fix use-after-free in ctnetlink_dump_exp_ct()
ctnetlink_dump_exp_ct() stores a conntrack pointer in cb->data for the netlink dump callback ctnetlink_exp_ct_dump_table(), but drops the conntrack reference immediately after netlink_dump_start(). When the dump spans multiple rounds, the second recvmsg() triggers the dump callback which dereferences the now-freed conntrack via nfct_help(ct), leading to a use-after-free on ct->ext.
The bug is that the netlink_dump_control has no .start or .done callbacks to manage the conntrack reference across dump rounds. Other dump functions in the same file (e.g. ctnetlink_get_conntrack) properly use .start/.done callbacks for this purpose.
Fix this by adding .start and .done callbacks that hold and release the conntrack reference for the duration of the dump, and move the nfct_help() call after the cb->args[0] early-return check in the dump callback to avoid dereferencing ct->ext unnecessarily.
BUG: KASAN: slab-use-after-free in ctnetlink_exp_ct_dump_table+0x4f/0x2e0 Read of size 8 at addr ffff88810597ebf0 by task ctnetlink_poc/133
CPU: 1 UID: 0 PID: 133 Comm: ctnetlink_poc Not tainted 7.0.0-rc2+ #3 PREEMPTLAZY Call Trace: ctnetlink_exp_ct_dump_table+0x4f/0x2e0 netlink_dump+0x333/0x880 netlink_recvmsg+0x3e2/0x4b0 ? aa_sk_perm+0x184/0x450 sock_recvmsg+0xde/0xf0
Allocated by task 133: kmem_cache_alloc_noprof+0x134/0x440 __nf_conntrack_alloc+0xa8/0x2b0 ctnetlink_create_conntrack+0xa1/0x900 ctnetlink_new_conntrack+0x3cf/0x7d0 nfnetlink_rcv_msg+0x48e/0x510 netlink_rcv_skb+0xc9/0x1f0 nfnetlink_rcv+0xdb/0x220 netlink_unicast+0x3ec/0x590 netlink_sendmsg+0x397/0x690 __sys_sendmsg+0xf4/0x180
Freed by task 0: slab_free_after_rcu_debug+0xad/0x1e0 rcu_core+0x5c3/0x9c0
{
"affected": [],
"aliases": [
"CVE-2026-23458"
],
"database_specific": {
"cwe_ids": [
"CWE-416"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-04-03T16:16:32Z",
"severity": "HIGH"
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\nnetfilter: ctnetlink: fix use-after-free in ctnetlink_dump_exp_ct()\n\nctnetlink_dump_exp_ct() stores a conntrack pointer in cb-\u003edata for the\nnetlink dump callback ctnetlink_exp_ct_dump_table(), but drops the\nconntrack reference immediately after netlink_dump_start(). When the\ndump spans multiple rounds, the second recvmsg() triggers the dump\ncallback which dereferences the now-freed conntrack via nfct_help(ct),\nleading to a use-after-free on ct-\u003eext.\n\nThe bug is that the netlink_dump_control has no .start or .done\ncallbacks to manage the conntrack reference across dump rounds. Other\ndump functions in the same file (e.g. ctnetlink_get_conntrack) properly\nuse .start/.done callbacks for this purpose.\n\nFix this by adding .start and .done callbacks that hold and release the\nconntrack reference for the duration of the dump, and move the\nnfct_help() call after the cb-\u003eargs[0] early-return check in the dump\ncallback to avoid dereferencing ct-\u003eext unnecessarily.\n\n BUG: KASAN: slab-use-after-free in ctnetlink_exp_ct_dump_table+0x4f/0x2e0\n Read of size 8 at addr ffff88810597ebf0 by task ctnetlink_poc/133\n\n CPU: 1 UID: 0 PID: 133 Comm: ctnetlink_poc Not tainted 7.0.0-rc2+ #3 PREEMPTLAZY\n Call Trace:\n \u003cTASK\u003e\n ctnetlink_exp_ct_dump_table+0x4f/0x2e0\n netlink_dump+0x333/0x880\n netlink_recvmsg+0x3e2/0x4b0\n ? aa_sk_perm+0x184/0x450\n sock_recvmsg+0xde/0xf0\n\n Allocated by task 133:\n kmem_cache_alloc_noprof+0x134/0x440\n __nf_conntrack_alloc+0xa8/0x2b0\n ctnetlink_create_conntrack+0xa1/0x900\n ctnetlink_new_conntrack+0x3cf/0x7d0\n nfnetlink_rcv_msg+0x48e/0x510\n netlink_rcv_skb+0xc9/0x1f0\n nfnetlink_rcv+0xdb/0x220\n netlink_unicast+0x3ec/0x590\n netlink_sendmsg+0x397/0x690\n __sys_sendmsg+0xf4/0x180\n\n Freed by task 0:\n slab_free_after_rcu_debug+0xad/0x1e0\n rcu_core+0x5c3/0x9c0",
"id": "GHSA-pqg4-x7w2-6f65",
"modified": "2026-10-15T03:35:31Z",
"published": "2026-04-03T18:31:22Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-23458"
},
{
"type": "WEB",
"url": "https://cert-portal.siemens.com/productcert/html/ssa-019113.html"
},
{
"type": "WEB",
"url": "https://cert-portal.siemens.com/productcert/html/ssa-082556.html"
},
{
"type": "WEB",
"url": "https://cert-portal.siemens.com/productcert/html/ssa-457936.html"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/04c8907ce4e3d3e26c5e1a3e47aa5d17082cbb56"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/5cb81eeda909dbb2def209dd10636b51549a3f8a"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/9821b47f669eb82791fa0b1a6ebaf9aa219bea72"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/bdf2724eefd4455a66863abb025bab8d3aa98c57"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/cd541f15b60e2257441398cf495d978f816d09f8"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/d8cd0efbccc5cfb0a80da744a7da76e1333ab925"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/f025171feef2ac65663d7986f1d5ff0c28d6b2a9"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/f04cc86d59906513d2d62183b882966fc0ae0390"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
"type": "CVSS_V3"
}
]
}
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