cbcvebase.
CVE-2025-68241
published 2025-12-16

CVE-2025-68241: In the Linux kernel, the following vulnerability has been resolved: ipv4: route: Prevent rt_bind_exception() from rebinding stale fnhe The sit driver's packet…

PriorityP340high7.5CVSS 3.1
AVNACLPRNUINSUCNINAH
EPSS
0.40%
33.2th percentile
In the Linux kernel, the following vulnerability has been resolved: ipv4: route: Prevent rt_bind_exception() from rebinding stale fnhe The sit driver's packet transmission path calls: sit_tunnel_xmit() -> update_or_create_fnhe(), which lead to fnhe_remove_oldest() being called to delete entries exceeding FNHE_RECLAIM_DEPTH+random. The race window is between fnhe_remove_oldest() selecting fnheX for deletion and the subsequent kfree_rcu(). During this time, the concurrent path's __mkroute_output() -> find_exception() can fetch the soon-to-be-deleted fnheX, and rt_bind_exception() then binds it with a new dst using a dst_hold(). When the original fnheX is freed via RCU, the dst reference remains permanently leaked. CPU 0 CPU 1 __mkroute_output() find_exception() [fnheX] update_or_create_fnhe() fnhe_remove_oldest() [fnheX] rt_bind_exception() [bind dst] RCU callback [fnheX freed, dst leak] This issue manifests as a device reference count leak and a warning in dmesg when unregistering the net device: unregister_netdevice: waiting for sitX to become free. Usage count = N Ido Schimmel provided the simple test validation method [1]. The fix clears 'oldest->fnhe_daddr' before calling fnhe_flush_routes(). Since rt_bind_exception() checks this field, setting it to zero prevents the stale fnhe from being reused and bound to a new dst just before it is freed. [1] ip netns add ns1 ip -n ns1 link set dev lo up ip -n ns1 address add 192.0.2.1/32 dev lo ip -n ns1 link add name dummy1 up type dummy ip -n ns1 route add 192.0.2.2/32 dev dummy1 ip -n ns1 link add name gretap1 up arp off type gretap \ local 192.0.2.1 remote 192.0.2.2 ip -n ns1 route add 198.51.0.0/16 dev gretap1 taskset -c 0 ip netns exec ns1 mausezahn gretap1 \ -A 198.51.100.1 -B 198.51.0.0/16 -t udp -p 1000 -c 0 -q & taskset -c 2 ip netns exec ns1 mausezahn gretap1 \ -A 198.51.100.1 -B 198.51.0.0/16 -t udp -p 1000 -c 0 -q & sleep 10 ip netns pids ns1 | xargs kill ip netns del ns1

Affected

43 ranges· showing 25
VendorProductVersion rangeFixed in
debianlinux< linux 6.1.159-1 (bookworm)linux 6.1.159-1 (bookworm)
debianlinux-6.1< linux 6.1.159-1 (bookworm)linux 6.1.159-1 (bookworm)
linuxlinux
linuxlinux
linuxlinux
linuxlinux
linuxlinux
linuxlinux
linuxlinux
linuxlinux>= 4.14.247 < 4.154.15
linuxlinux>= 4.19.207 < 4.204.20
linuxlinux>= 4.4.284 < 4.54.5
linuxlinux>= 4.9.283 < 4.104.10
linuxlinux>= 5.10.65 < 5.10.2475.10.247
linuxlinux>= 5.13.17 < 5.145.14
linuxlinux>= 5.14.4 < 5.155.15
linuxlinux>= 5.4.146 < 5.4.3025.4.302
linuxlinux>= 5867e20e1808acd0c832ddea2587e5ee49813874 < 4b7210da22429765d19460d38c30eeca726562824b7210da22429765d19460d38c30eeca72656282
linuxlinux>= 67d6d681e15b578c1725bad8ad079e05d1c48a8e < 298f1e0694ab4edb6092d66efed93c4554e6ced1298f1e0694ab4edb6092d66efed93c4554e6ced1
linuxlinux>= 67d6d681e15b578c1725bad8ad079e05d1c48a8e < b8a44407bdaf2f0c5505cc7d9fc7d8da90cf9a94b8a44407bdaf2f0c5505cc7d9fc7d8da90cf9a94
linuxlinux>= 67d6d681e15b578c1725bad8ad079e05d1c48a8e < 041ab9ca6e80d8f792bb69df28ebf1ef39c06af8041ab9ca6e80d8f792bb69df28ebf1ef39c06af8
linuxlinux>= 67d6d681e15b578c1725bad8ad079e05d1c48a8e < b84f083f50ecc736a95091691339a1b363962f0eb84f083f50ecc736a95091691339a1b363962f0e
linuxlinux>= 67d6d681e15b578c1725bad8ad079e05d1c48a8e < 0fd16ed6dc331636fb2a874c42d2f7d3156f7ff00fd16ed6dc331636fb2a874c42d2f7d3156f7ff0
linuxlinux>= 67d6d681e15b578c1725bad8ad079e05d1c48a8e < ac1499fcd40fe06479e9b933347b837ccabc2a40ac1499fcd40fe06479e9b933347b837ccabc2a40
linuxlinux>= e46e23c289f62ccd8e2230d9ce652072d777ff30 < 69d35c12168f9c59b159ae566f77dfad9f96d7ca69d35c12168f9c59b159ae566f77dfad9f96d7ca

CVSS provenance

nvdv3.17.5HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
osv7.8HIGH
vendor_ubuntu7.8HIGH
vendor_redhat4.7MEDIUM
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