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 drive...

Description

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

Metrics

CVSS 3.1

7.5/10

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

EPSS Probability

0.17%

6.8th percentile

Probability of exploitation in the next 30 days. Learn more

Affected Software

Source: CNA advisory (CVE.org). NVD analysis pending.

Vendor	Product	Versions
Linux	Linux	>= e46e23c289f62ccd8e2230d9ce652072d777ff30, < 69d35c12168f9c59b159ae566f77dfad9f96d7ca; >= 5867e20e1808acd0c832ddea2587e5ee49813874, < 4b7210da22429765d19460d38c30eeca72656282; >= 67d6d681e15b578c1725bad8ad079e05d1c48a8e, < 298f1e0694ab4edb6092d66efed93c4554e6ced1; >= 67d6d681e15b578c1725bad8ad079e05d1c48a8e, < b8a44407bdaf2f0c5505cc7d9fc7d8da90cf9a94; >= 67d6d681e15b578c1725bad8ad079e05d1c48a8e, < 041ab9ca6e80d8f792bb69df28ebf1ef39c06af8; >= 67d6d681e15b578c1725bad8ad079e05d1c48a8e, < b84f083f50ecc736a95091691339a1b363962f0e; >= 67d6d681e15b578c1725bad8ad079e05d1c48a8e, < 0fd16ed6dc331636fb2a874c42d2f7d3156f7ff0; >= 67d6d681e15b578c1725bad8ad079e05d1c48a8e, < ac1499fcd40fe06479e9b933347b837ccabc2a40; bed8941fbdb72a61f6348c4deb0db69c4de87aca; f10ce783bcc4d8ea454563a7d56ae781640e7dcb; f484595be6b7ef9d095a32becabb5dae8204fb2a; 3e6bd2b583f18da9856fc9741ffa200a74a52cba; 5ae06218331f39ec45b5d039aa7cb3ddd4bb8008; 4589a12dcf80af31137ef202be1ff4a321707a73; >= 5.4.146, < 5.4.302; >= 5.10.65, < 5.10.247; >= 4.4.284, < 4.5; >= 4.9.283, < 4.10; >= 4.14.247, < 4.15; >= 4.19.207, < 4.20; >= 5.13.17, < 5.14; >= 5.14.4, < 5.15
Linux	Linux	5.15

References

Timeline

Published: Dec 16, 2025
Last Modified: Jul 30, 2026
Status: Deferred

Frequently Asked Questions

What is 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 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

How severe is CVE-2025-68241?

CVE-2025-68241 has a CVSS score of 7.5/10 (HIGH severity). The EPSS model estimates a 0.17% probability of exploitation in the next 30 days.

How do I fix CVE-2025-68241?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

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