{"id":"CVE-2025-68241","title":"In the Linux kernel, the following vulnerability has been resolved:\n\nipv4: route: Prevent rt_bind_exception() from rebinding stale fnhe\n\nThe sit driver's packet transmission path calls: sit_tunnel_xmit() ->\nupdate_or_create_fnhe(), which…","summary":"In the Linux kernel, the following vulnerability has been resolved:\n\nipv4: route: Prevent rt_bind_exception() from rebinding stale fnhe\n\nThe sit driver's packet transmission path calls: sit_tunnel_xmit() ->\nupdate_or_create_fnhe(), which…","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","published":"2025-12-16","updated":"2026-10-14","sourceUpdated":"2026-10-14T13:10:00.187","source":"NVD","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2025-68241","references":[{"url":"https://git.kernel.org/stable/c/041ab9ca6e80d8f792bb69df28ebf1ef39c06af8","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/0fd16ed6dc331636fb2a874c42d2f7d3156f7ff0","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/298f1e0694ab4edb6092d66efed93c4554e6ced1","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/4b7210da22429765d19460d38c30eeca72656282","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/69d35c12168f9c59b159ae566f77dfad9f96d7ca","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/ac1499fcd40fe06479e9b933347b837ccabc2a40","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/b84f083f50ecc736a95091691339a1b363962f0e","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/b8a44407bdaf2f0c5505cc7d9fc7d8da90cf9a94","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"}],"tags":["nvd"],"epss":0.00466,"epssPercentile":0.38568,"ingestedAt":"2026-10-14T13:30:58.464Z","slug":"CVE-2025-68241","body":"## Overview\n\nIn the Linux kernel, the following vulnerability has been resolved:\n\nipv4: route: Prevent rt_bind_exception() from rebinding stale fnhe\n\nThe sit driver's packet transmission path calls: sit_tunnel_xmit() ->\nupdate_or_create_fnhe(), which lead to fnhe_remove_oldest() being called\nto delete entries exceeding FNHE_RECLAIM_DEPTH+random.\n\nThe race window is between fnhe_remove_oldest() selecting fnheX for\ndeletion and the subsequent kfree_rcu(). During this time, the\nconcurrent path's __mkroute_output() -> find_exception() can fetch the\nsoon-to-be-deleted fnheX, and rt_bind_exception() then binds it with a\nnew dst using a dst_hold(). When the original fnheX is freed via RCU,\nthe dst reference remains permanently leaked.\n\nCPU 0                             CPU 1\n__mkroute_output()\n  find_exception() [fnheX]\n                                  update_or_create_fnhe()\n                                    fnhe_remove_oldest() [fnheX]\n  rt_bind_exception() [bind dst]\n                                  RCU callback [fnheX freed, dst leak]\n\nThis issue manifests as a device reference count leak and a warning in\ndmesg when unregistering the net device:\n\n  unregister_netdevice: waiting for sitX to become free. Usage count = N\n\nIdo Schimmel provided the simple test validation method [1].\n\nThe fix clears 'oldest->fnhe_daddr' before calling fnhe_flush_routes().\nSince rt_bind_exception() checks this field, setting it to zero prevents\nthe stale fnhe from being reused and bound to a new dst just before it\nis freed.\n\n[1]\nip netns add ns1\nip -n ns1 link set dev lo up\nip -n ns1 address add 192.0.2.1/32 dev lo\nip -n ns1 link add name dummy1 up type dummy\nip -n ns1 route add 192.0.2.2/32 dev dummy1\nip -n ns1 link add name gretap1 up arp off type gretap \\\n    local 192.0.2.1 remote 192.0.2.2\nip -n ns1 route add 198.51.0.0/16 dev gretap1\ntaskset -c 0 ip netns exec ns1 mausezahn gretap1 \\\n    -A 198.51.100.1 -B 198.51.0.0/16 -t udp -p 1000 -c 0 -q &\ntaskset -c 2 ip netns exec ns1 mausezahn gretap1 \\\n    -A 198.51.100.1 -B 198.51.0.0/16 -t udp -p 1000 -c 0 -q &\nsleep 10\nip netns pids ns1 | xargs kill\nip netns del ns1\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":[]}