CVE-2025-39894
Estado: ModificadaMedia (5.5)—
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.
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.
Leer descripción completaMostrar menos
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.
Detalles técnicos trazas, registros y código del informe original
------------[ 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: <TASK> 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 </TASK> ---[ end trace 0000000000000000 ]---
CVSS
- Versión: 3.1
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
- Puntuación base: 5.5
Probabilidad de explotación (EPSS)
- Probabilidad de explotación en los próximos 30 días: 0.32%
- Percentil entre todas las CVEs puntuadas: 23
- Fecha de la puntuación: 6/10/2026
EPSS (Exploit Prediction Scoring System, de FIRST) estima la probabilidad de que una vulnerabilidad sea explotada en 30 días. Complementa a CVSS (impacto) y a CISA KEV (explotación confirmada).
Tecnologías afectadas (2)
CWE
- NVD-CWE-noinfo
Referencias
- https://git.kernel.org/stable/c/479a54ab92087318514c82428a87af2d7af1a576
- https://git.kernel.org/stable/c/50db11e2bbb635e38e3dd096215580d6adb41fb0
- https://git.kernel.org/stable/c/a74abcf0f09f59daeecf7a3ba9c1d690808b0afe
- https://git.kernel.org/stable/c/c47ca77fee9071aa543bae592dd2a384f895c8b6
- https://git.kernel.org/stable/c/ccbad4803225eafe0175d3cb19f0d8d73b504a94
- https://git.kernel.org/stable/c/d00c8b0daf56012f69075e3377da67878c775e4c
- https://lists.debian.org/debian-lts-announce/2025/10/msg00008.html
JSON original (NVD)
Mostrar
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"value": "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 <TASK>\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 </TASK>\n ---[ end trace 0000000000000000 ]---\n\nTo solve the hash conflict, nf_ct_resolve_clash() try to merge the\nconntracks, and update skb->_nfct. However, br_nf_local_in() still use the\nold ct from local variable 'nfct' 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."
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