CVE-2025-68241 (GCVE-0-2025-68241)
Vulnerability from cvelistv5
Published
2025-12-16 14:21
Modified
2025-12-16 14:21
Severity ?
VLAI Severity ?
EPSS score ?
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 | ||
|---|---|---|---|---|
| Linux | Linux |
Version: e46e23c289f62ccd8e2230d9ce652072d777ff30 Version: 5867e20e1808acd0c832ddea2587e5ee49813874 Version: 67d6d681e15b578c1725bad8ad079e05d1c48a8e Version: 67d6d681e15b578c1725bad8ad079e05d1c48a8e Version: 67d6d681e15b578c1725bad8ad079e05d1c48a8e Version: 67d6d681e15b578c1725bad8ad079e05d1c48a8e Version: 67d6d681e15b578c1725bad8ad079e05d1c48a8e Version: 67d6d681e15b578c1725bad8ad079e05d1c48a8e Version: bed8941fbdb72a61f6348c4deb0db69c4de87aca Version: f10ce783bcc4d8ea454563a7d56ae781640e7dcb Version: f484595be6b7ef9d095a32becabb5dae8204fb2a Version: 3e6bd2b583f18da9856fc9741ffa200a74a52cba Version: 5ae06218331f39ec45b5d039aa7cb3ddd4bb8008 Version: 4589a12dcf80af31137ef202be1ff4a321707a73 |
||
{
"containers": {
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{
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},
{
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{
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}
]
},
{
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"product": "Linux",
"programFiles": [
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],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"versions": [
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},
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"version": "0",
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},
{
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},
{
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{
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},
{
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},
{
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"version": "6.18",
"versionType": "original_commit_for_fix"
}
]
}
],
"cpeApplicability": [
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],
"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"
}
],
"providerMetadata": {
"dateUpdated": "2025-12-16T14:21:18.682Z",
"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"shortName": "Linux"
},
"references": [
{
"url": "https://git.kernel.org/stable/c/69d35c12168f9c59b159ae566f77dfad9f96d7ca"
},
{
"url": "https://git.kernel.org/stable/c/4b7210da22429765d19460d38c30eeca72656282"
},
{
"url": "https://git.kernel.org/stable/c/298f1e0694ab4edb6092d66efed93c4554e6ced1"
},
{
"url": "https://git.kernel.org/stable/c/b8a44407bdaf2f0c5505cc7d9fc7d8da90cf9a94"
},
{
"url": "https://git.kernel.org/stable/c/041ab9ca6e80d8f792bb69df28ebf1ef39c06af8"
},
{
"url": "https://git.kernel.org/stable/c/b84f083f50ecc736a95091691339a1b363962f0e"
},
{
"url": "https://git.kernel.org/stable/c/0fd16ed6dc331636fb2a874c42d2f7d3156f7ff0"
},
{
"url": "https://git.kernel.org/stable/c/ac1499fcd40fe06479e9b933347b837ccabc2a40"
}
],
"title": "ipv4: route: Prevent rt_bind_exception() from rebinding stale fnhe",
"x_generator": {
"engine": "bippy-1.2.0"
}
}
},
"cveMetadata": {
"assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"assignerShortName": "Linux",
"cveId": "CVE-2025-68241",
"datePublished": "2025-12-16T14:21:18.682Z",
"dateReserved": "2025-12-16T13:41:40.263Z",
"dateUpdated": "2025-12-16T14:21:18.682Z",
"state": "PUBLISHED"
},
"dataType": "CVE_RECORD",
"dataVersion": "5.2",
"vulnerability-lookup:meta": {
"nvd": "{\"cve\":{\"id\":\"CVE-2025-68241\",\"sourceIdentifier\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"published\":\"2025-12-16T15:15:53.283\",\"lastModified\":\"2025-12-18T15:08:06.237\",\"vulnStatus\":\"Awaiting Analysis\",\"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\"}],\"metrics\":{},\"references\":[{\"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\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"}]}}"
}
}
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Sightings
| Author | Source | Type | Date |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or seen somewhere by the user.
- Confirmed: The vulnerability is confirmed from an analyst perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: This vulnerability was exploited and seen by the user reporting the sighting.
- Patched: This vulnerability was successfully patched by the user reporting the sighting.
- Not exploited: This vulnerability was not exploited or seen by the user reporting the sighting.
- Not confirmed: The user expresses doubt about the veracity of the vulnerability.
- Not patched: This vulnerability was not successfully patched by the user reporting the sighting.
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