FKIE_CVE-2025-68241
Vulnerability from fkie_nvd - Published: 2025-12-16 15:15 - Updated: 2026-06-17 09:58
Severity
Summary
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
References
Impacted products
| Vendor | Product | Version |
|---|
{
"affected": [
{
"affectedData": [
{
"defaultStatus": "unaffected",
"product": "Linux",
"programFiles": [
"net/ipv4/route.c"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"versions": [
{
"lessThan": "69d35c12168f9c59b159ae566f77dfad9f96d7ca",
"status": "affected",
"version": "e46e23c289f62ccd8e2230d9ce652072d777ff30",
"versionType": "git"
},
{
"lessThan": "4b7210da22429765d19460d38c30eeca72656282",
"status": "affected",
"version": "5867e20e1808acd0c832ddea2587e5ee49813874",
"versionType": "git"
},
{
"lessThan": "298f1e0694ab4edb6092d66efed93c4554e6ced1",
"status": "affected",
"version": "67d6d681e15b578c1725bad8ad079e05d1c48a8e",
"versionType": "git"
},
{
"lessThan": "b8a44407bdaf2f0c5505cc7d9fc7d8da90cf9a94",
"status": "affected",
"version": "67d6d681e15b578c1725bad8ad079e05d1c48a8e",
"versionType": "git"
},
{
"lessThan": "041ab9ca6e80d8f792bb69df28ebf1ef39c06af8",
"status": "affected",
"version": "67d6d681e15b578c1725bad8ad079e05d1c48a8e",
"versionType": "git"
},
{
"lessThan": "b84f083f50ecc736a95091691339a1b363962f0e",
"status": "affected",
"version": "67d6d681e15b578c1725bad8ad079e05d1c48a8e",
"versionType": "git"
},
{
"lessThan": "0fd16ed6dc331636fb2a874c42d2f7d3156f7ff0",
"status": "affected",
"version": "67d6d681e15b578c1725bad8ad079e05d1c48a8e",
"versionType": "git"
},
{
"lessThan": "ac1499fcd40fe06479e9b933347b837ccabc2a40",
"status": "affected",
"version": "67d6d681e15b578c1725bad8ad079e05d1c48a8e",
"versionType": "git"
},
{
"status": "affected",
"version": "bed8941fbdb72a61f6348c4deb0db69c4de87aca",
"versionType": "git"
},
{
"status": "affected",
"version": "f10ce783bcc4d8ea454563a7d56ae781640e7dcb",
"versionType": "git"
},
{
"status": "affected",
"version": "f484595be6b7ef9d095a32becabb5dae8204fb2a",
"versionType": "git"
},
{
"status": "affected",
"version": "3e6bd2b583f18da9856fc9741ffa200a74a52cba",
"versionType": "git"
},
{
"status": "affected",
"version": "5ae06218331f39ec45b5d039aa7cb3ddd4bb8008",
"versionType": "git"
},
{
"status": "affected",
"version": "4589a12dcf80af31137ef202be1ff4a321707a73",
"versionType": "git"
},
{
"lessThan": "5.4.302",
"status": "affected",
"version": "5.4.146",
"versionType": "semver"
},
{
"lessThan": "5.10.247",
"status": "affected",
"version": "5.10.65",
"versionType": "semver"
},
{
"lessThan": "4.5",
"status": "affected",
"version": "4.4.284",
"versionType": "semver"
},
{
"lessThan": "4.10",
"status": "affected",
"version": "4.9.283",
"versionType": "semver"
},
{
"lessThan": "4.15",
"status": "affected",
"version": "4.14.247",
"versionType": "semver"
},
{
"lessThan": "4.20",
"status": "affected",
"version": "4.19.207",
"versionType": "semver"
},
{
"lessThan": "5.14",
"status": "affected",
"version": "5.13.17",
"versionType": "semver"
},
{
"lessThan": "5.15",
"status": "affected",
"version": "5.14.4",
"versionType": "semver"
}
]
},
{
"defaultStatus": "affected",
"product": "Linux",
"programFiles": [
"net/ipv4/route.c"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"versions": [
{
"status": "affected",
"version": "5.15"
},
{
"lessThan": "5.15",
"status": "unaffected",
"version": "0",
"versionType": "semver"
},
{
"lessThanOrEqual": "5.4.*",
"status": "unaffected",
"version": "5.4.302",
"versionType": "semver"
},
{
"lessThanOrEqual": "5.10.*",
"status": "unaffected",
"version": "5.10.247",
"versionType": "semver"
},
{
"lessThanOrEqual": "5.15.*",
"status": "unaffected",
"version": "5.15.197",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.1.*",
"status": "unaffected",
"version": "6.1.159",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.6.*",
"status": "unaffected",
"version": "6.6.117",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.12.*",
"status": "unaffected",
"version": "6.12.59",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.17.*",
"status": "unaffected",
"version": "6.17.9",
"versionType": "semver"
},
{
"lessThanOrEqual": "*",
"status": "unaffected",
"version": "6.18",
"versionType": "original_commit_for_fix"
}
]
}
],
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
}
],
"cveTags": [],
"descriptions": [
{
"lang": "en",
"value": "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\u0027s packet transmission path calls: sit_tunnel_xmit() -\u003e\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\u0027s __mkroute_output() -\u003e 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 \u0027oldest-\u003efnhe_daddr\u0027 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 \u0026\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 \u0026\nsleep 10\nip netns pids ns1 | xargs kill\nip netns del ns1"
}
],
"id": "CVE-2025-68241",
"lastModified": "2026-06-17T09:58:47.443",
"metrics": {
"ssvcV203": [
{
"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
"ssvcData": {
"id": "CVE-2025-68241",
"options": [
{
"exploitation": "none"
},
{
"automatable": "no"
},
{
"technicalImpact": "partial"
}
],
"role": "CISA Coordinator",
"timestamp": "2026-06-16T16:24:01.270292Z",
"version": "2.0.3"
}
}
]
},
"published": "2025-12-16T15:15:53.283",
"references": [
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"url": "https://git.kernel.org/stable/c/041ab9ca6e80d8f792bb69df28ebf1ef39c06af8"
},
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"url": "https://git.kernel.org/stable/c/0fd16ed6dc331636fb2a874c42d2f7d3156f7ff0"
},
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"url": "https://git.kernel.org/stable/c/298f1e0694ab4edb6092d66efed93c4554e6ced1"
},
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"url": "https://git.kernel.org/stable/c/4b7210da22429765d19460d38c30eeca72656282"
},
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"url": "https://git.kernel.org/stable/c/69d35c12168f9c59b159ae566f77dfad9f96d7ca"
},
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"url": "https://git.kernel.org/stable/c/ac1499fcd40fe06479e9b933347b837ccabc2a40"
},
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"url": "https://git.kernel.org/stable/c/b84f083f50ecc736a95091691339a1b363962f0e"
},
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"url": "https://git.kernel.org/stable/c/b8a44407bdaf2f0c5505cc7d9fc7d8da90cf9a94"
}
],
"sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"vulnStatus": "Deferred"
}
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Experimental. This forecast is provided for visualization only and may change without notice. Do not use it for operational decisions.
Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
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