{"id":"AZL-74745","summary":"CVE-2025-39894 affecting package kernel for versions less than 5.15.200.1-1","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":"2026-04-01T05:22:45.512014Z","published":"2025-10-01T08:15:31Z","upstream":["CVE-2025-39894"],"references":[{"type":"WEB","url":"https://nvd.nist.gov/vuln/detail/CVE-2025-39894"}],"affected":[{"package":{"name":"kernel","ecosystem":"Azure Linux:2","purl":"pkg:rpm/azure-linux/kernel"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"5.15.200.1-1"}]}],"database_specific":{"source":"https://github.com/microsoft/AzureLinuxVulnerabilityData/blob/main/osv/AZL-74745.json"}}],"schema_version":"1.7.5"}