ghsa-rq7c-gx2v-c384
Vulnerability from github
In the Linux kernel, the following vulnerability has been resolved:
netfilter: br_netfilter: do not check confirmed bit in br_nf_local_in() after confirm
When send a broadcast packet to a tap device, which was added to a bridge, br_nf_local_in() is called to confirm the conntrack. If another conntrack with the same hash value is added to the hash table, which can be triggered by a normal packet to a non-bridge device, the below warning may happen.
------------[ cut here ]------------ WARNING: CPU: 1 PID: 96 at net/bridge/br_netfilter_hooks.c:632 br_nf_local_in+0x168/0x200 CPU: 1 UID: 0 PID: 96 Comm: tap_send Not tainted 6.17.0-rc2-dirty #44 PREEMPT(voluntary) RIP: 0010:br_nf_local_in+0x168/0x200 Call Trace: nf_hook_slow+0x3e/0xf0 br_pass_frame_up+0x103/0x180 br_handle_frame_finish+0x2de/0x5b0 br_nf_hook_thresh+0xc0/0x120 br_nf_pre_routing_finish+0x168/0x3a0 br_nf_pre_routing+0x237/0x5e0 br_handle_frame+0x1ec/0x3c0 __netif_receive_skb_core+0x225/0x1210 __netif_receive_skb_one_core+0x37/0xa0 netif_receive_skb+0x36/0x160 tun_get_user+0xa54/0x10c0 tun_chr_write_iter+0x65/0xb0 vfs_write+0x305/0x410 ksys_write+0x60/0xd0 do_syscall_64+0xa4/0x260 entry_SYSCALL_64_after_hwframe+0x77/0x7f ---[ end trace 0000000000000000 ]---
To solve the hash conflict, nf_ct_resolve_clash() try to merge the conntracks, and update skb->_nfct. However, br_nf_local_in() still use the old ct from local variable 'nfct' after confirm(), which leads to this warning.
If confirm() does not insert the conntrack entry and return NF_DROP, the warning may also occur. There is no need to reserve the WARN_ON_ONCE, just remove it.
{
"affected": [],
"aliases": [
"CVE-2025-39894"
],
"database_specific": {
"cwe_ids": [],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2025-10-01T08:15:31Z",
"severity": null
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\nnetfilter: br_netfilter: do not check confirmed bit in br_nf_local_in() after confirm\n\nWhen send a broadcast packet to a tap device, which was added to a bridge,\nbr_nf_local_in() is called to confirm the conntrack. If another conntrack\nwith the same hash value is added to the hash table, which can be\ntriggered by a normal packet to a non-bridge device, the below warning\nmay happen.\n\n ------------[ cut here ]------------\n WARNING: CPU: 1 PID: 96 at net/bridge/br_netfilter_hooks.c:632 br_nf_local_in+0x168/0x200\n CPU: 1 UID: 0 PID: 96 Comm: tap_send Not tainted 6.17.0-rc2-dirty #44 PREEMPT(voluntary)\n RIP: 0010:br_nf_local_in+0x168/0x200\n Call Trace:\n \u003cTASK\u003e\n nf_hook_slow+0x3e/0xf0\n br_pass_frame_up+0x103/0x180\n br_handle_frame_finish+0x2de/0x5b0\n br_nf_hook_thresh+0xc0/0x120\n br_nf_pre_routing_finish+0x168/0x3a0\n br_nf_pre_routing+0x237/0x5e0\n br_handle_frame+0x1ec/0x3c0\n __netif_receive_skb_core+0x225/0x1210\n __netif_receive_skb_one_core+0x37/0xa0\n netif_receive_skb+0x36/0x160\n tun_get_user+0xa54/0x10c0\n tun_chr_write_iter+0x65/0xb0\n vfs_write+0x305/0x410\n ksys_write+0x60/0xd0\n do_syscall_64+0xa4/0x260\n entry_SYSCALL_64_after_hwframe+0x77/0x7f\n \u003c/TASK\u003e\n ---[ end trace 0000000000000000 ]---\n\nTo solve the hash conflict, nf_ct_resolve_clash() try to merge the\nconntracks, and update skb-\u003e_nfct. However, br_nf_local_in() still use the\nold ct from local variable \u0027nfct\u0027 after confirm(), which leads to this\nwarning.\n\nIf confirm() does not insert the conntrack entry and return NF_DROP, the\nwarning may also occur. There is no need to reserve the WARN_ON_ONCE, just\nremove it.",
"id": "GHSA-rq7c-gx2v-c384",
"modified": "2025-10-01T09:30:24Z",
"published": "2025-10-01T09:30:24Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2025-39894"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/479a54ab92087318514c82428a87af2d7af1a576"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/50db11e2bbb635e38e3dd096215580d6adb41fb0"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/a74abcf0f09f59daeecf7a3ba9c1d690808b0afe"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/c47ca77fee9071aa543bae592dd2a384f895c8b6"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/ccbad4803225eafe0175d3cb19f0d8d73b504a94"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/d00c8b0daf56012f69075e3377da67878c775e4c"
}
],
"schema_version": "1.4.0",
"severity": []
}
Sightings
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