{"id":"CVE-2025-39894","title":"netfilter: br_netfilter: do not check confirmed bit in br_nf_local_in() after confirm","summary":"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_…","severity":"high","cvss":7.5,"cvssVector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","cvssSource":"cna","vendor":"Linux","product":"Linux","affected":["Linux >= 7c3f28599652acf431a2211168de4a583f30b6d5 < d00c8b0daf56012f69075e3377da67878c775e4c","Linux >= 2b1414d5e94e477edff1d2c79030f1d742625ea0 < ccbad4803225eafe0175d3cb19f0d8d73b504a94","Linux >= 80cd0487f630b5382734997c3e5e3003a77db315 < 50db11e2bbb635e38e3dd096215580d6adb41fb0","Linux >= 62e7151ae3eb465e0ab52a20c941ff33bb6332e9 < c47ca77fee9071aa543bae592dd2a384f895c8b6","Linux >= 62e7151ae3eb465e0ab52a20c941ff33bb6332e9 < a74abcf0f09f59daeecf7a3ba9c1d690808b0afe","Linux >= 62e7151ae3eb465e0ab52a20c941ff33bb6332e9 < 479a54ab92087318514c82428a87af2d7af1a576","Linux cb734975b0ffa688ff6cc0eed463865bf07b6c01","Linux >= 5.15.151 < 5.15.192","Linux >= 6.1.81 < 6.1.151","Linux >= 6.6.21 < 6.6.105","Linux >= 6.7.9 < 6.8","Linux 6.8"],"ssvc":{"exploitation":"none","automatable":"yes","technicalImpact":"partial","timestamp":"2026-10-15T21:54:35.991421Z"},"published":"2025-10-01","updated":"2026-10-15","sourceUpdated":"2026-10-15T22:02:32.869Z","source":"CVEORG","sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2025-39894","references":[{"url":"https://git.kernel.org/stable/c/d00c8b0daf56012f69075e3377da67878c775e4c"},{"url":"https://git.kernel.org/stable/c/ccbad4803225eafe0175d3cb19f0d8d73b504a94"},{"url":"https://git.kernel.org/stable/c/50db11e2bbb635e38e3dd096215580d6adb41fb0"},{"url":"https://git.kernel.org/stable/c/c47ca77fee9071aa543bae592dd2a384f895c8b6"},{"url":"https://git.kernel.org/stable/c/a74abcf0f09f59daeecf7a3ba9c1d690808b0afe"},{"url":"https://git.kernel.org/stable/c/479a54ab92087318514c82428a87af2d7af1a576"}],"tags":["cve.org"],"epss":0.00332,"epssPercentile":0.26196,"ingestedAt":"2026-10-15T22:48:25.529Z","slug":"CVE-2025-39894","body":"## Overview\n\nIn 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.\n\n## Affected\n\n- `Linux >= 7c3f28599652acf431a2211168de4a583f30b6d5 < d00c8b0daf56012f69075e3377da67878c775e4c`\n- `Linux >= 2b1414d5e94e477edff1d2c79030f1d742625ea0 < ccbad4803225eafe0175d3cb19f0d8d73b504a94`\n- `Linux >= 80cd0487f630b5382734997c3e5e3003a77db315 < 50db11e2bbb635e38e3dd096215580d6adb41fb0`\n- `Linux >= 62e7151ae3eb465e0ab52a20c941ff33bb6332e9 < c47ca77fee9071aa543bae592dd2a384f895c8b6`\n- `Linux >= 62e7151ae3eb465e0ab52a20c941ff33bb6332e9 < a74abcf0f09f59daeecf7a3ba9c1d690808b0afe`\n- `Linux >= 62e7151ae3eb465e0ab52a20c941ff33bb6332e9 < 479a54ab92087318514c82428a87af2d7af1a576`\n- `Linux cb734975b0ffa688ff6cc0eed463865bf07b6c01`\n- `Linux >= 5.15.151 < 5.15.192`\n- `Linux >= 6.1.81 < 6.1.151`\n- `Linux >= 6.6.21 < 6.6.105`\n- `Linux >= 6.7.9 < 6.8`\n- `Linux 6.8`\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.","depth":"twilight","depthScore":41,"depthScoreParts":{"impact":41.3,"likelihood":0.1,"exploitation":0,"ransomware":0},"changes":[]}