FKIE_CVE-2025-39894

Vulnerability from fkie_nvd - Published: 2025-10-01 08:15 - Updated: 2026-01-16 19:30
Severity ?
5.5 (Medium) - CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Summary
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: <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 ]--- 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.
References
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/479a54ab92087318514c82428a87af2d7af1a576Patch
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/50db11e2bbb635e38e3dd096215580d6adb41fb0Patch
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/a74abcf0f09f59daeecf7a3ba9c1d690808b0afePatch
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/c47ca77fee9071aa543bae592dd2a384f895c8b6Patch
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/ccbad4803225eafe0175d3cb19f0d8d73b504a94Patch
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/d00c8b0daf56012f69075e3377da67878c775e4cPatch
af854a3a-2127-422b-91ae-364da2661108https://lists.debian.org/debian-lts-announce/2025/10/msg00008.htmlThird Party Advisory
Impacted products
Vendor Product Version
linux linux_kernel *
linux linux_kernel *
linux linux_kernel *
linux linux_kernel *
linux linux_kernel *
linux linux_kernel *
linux linux_kernel 6.8
linux linux_kernel 6.8
linux linux_kernel 6.17
linux linux_kernel 6.17
linux linux_kernel 6.17
linux linux_kernel 6.17
debian debian_linux 11.0
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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   \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."
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  "id": "CVE-2025-39894",
  "lastModified": "2026-01-16T19:30:25.443",
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          "baseScore": 5.5,
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          "confidentialityImpact": "NONE",
          "integrityImpact": "NONE",
          "privilegesRequired": "LOW",
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