{"id":"CVE-2025-39894","summary":"netfilter: br_netfilter: do not check confirmed bit in br_nf_local_in() after confirm","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 '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.","modified":"2026-04-02T12:48:11.998767Z","published":"2025-10-01T07:42:43.126Z","database_specific":{"cna_assigner":"Linux","osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2025/39xxx/CVE-2025-39894.json"},"references":[{"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"},{"type":"WEB","url":"https://lists.debian.org/debian-lts-announce/2025/10/msg00008.html"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2025/39xxx/CVE-2025-39894.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2025-39894"},{"type":"PACKAGE","url":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"7c3f28599652acf431a2211168de4a583f30b6d5"},{"fixed":"d00c8b0daf56012f69075e3377da67878c775e4c"}]},{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"2b1414d5e94e477edff1d2c79030f1d742625ea0"},{"fixed":"ccbad4803225eafe0175d3cb19f0d8d73b504a94"}]},{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"80cd0487f630b5382734997c3e5e3003a77db315"},{"fixed":"50db11e2bbb635e38e3dd096215580d6adb41fb0"}]},{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"62e7151ae3eb465e0ab52a20c941ff33bb6332e9"},{"fixed":"c47ca77fee9071aa543bae592dd2a384f895c8b6"},{"fixed":"a74abcf0f09f59daeecf7a3ba9c1d690808b0afe"},{"fixed":"479a54ab92087318514c82428a87af2d7af1a576"}]},{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"0"},{"last_affected":"cb734975b0ffa688ff6cc0eed463865bf07b6c01"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2025-39894.json"}}],"schema_version":"1.7.5"}