CVE-2025-38721 (GCVE-0-2025-38721)
Vulnerability from cvelistv5
Published
2025-09-04 15:33
Modified
2025-09-04 15:33
Severity ?
VLAI Severity ?
EPSS score ?
Summary
In the Linux kernel, the following vulnerability has been resolved:
netfilter: ctnetlink: fix refcount leak on table dump
There is a reference count leak in ctnetlink_dump_table():
if (res < 0) {
nf_conntrack_get(&ct->ct_general); // HERE
cb->args[1] = (unsigned long)ct;
...
While its very unlikely, its possible that ct == last.
If this happens, then the refcount of ct was already incremented.
This 2nd increment is never undone.
This prevents the conntrack object from being released, which in turn
keeps prevents cnet->count from dropping back to 0.
This will then block the netns dismantle (or conntrack rmmod) as
nf_conntrack_cleanup_net_list() will wait forever.
This can be reproduced by running conntrack_resize.sh selftest in a loop.
It takes ~20 minutes for me on a preemptible kernel on average before
I see a runaway kworker spinning in nf_conntrack_cleanup_net_list.
One fix would to change this to:
if (res < 0) {
if (ct != last)
nf_conntrack_get(&ct->ct_general);
But this reference counting isn't needed in the first place.
We can just store a cookie value instead.
A followup patch will do the same for ctnetlink_exp_dump_table,
it looks to me as if this has the same problem and like
ctnetlink_dump_table, we only need a 'skip hint', not the actual
object so we can apply the same cookie strategy there as well.
References
Impacted products
| Vendor | Product | Version | |||||||
|---|---|---|---|---|---|---|---|---|---|
| ▼ | Linux | Linux |
Version: d205dc40798d97d63ad348bfaf7394f445d152d4 Version: d205dc40798d97d63ad348bfaf7394f445d152d4 Version: d205dc40798d97d63ad348bfaf7394f445d152d4 Version: d205dc40798d97d63ad348bfaf7394f445d152d4 Version: d205dc40798d97d63ad348bfaf7394f445d152d4 Version: d205dc40798d97d63ad348bfaf7394f445d152d4 Version: d205dc40798d97d63ad348bfaf7394f445d152d4 Version: d205dc40798d97d63ad348bfaf7394f445d152d4 Version: d205dc40798d97d63ad348bfaf7394f445d152d4 |
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|
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{
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{
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{
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},
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}
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}
],
"cpeApplicability": [
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"descriptions": [
{
"lang": "en",
"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnetfilter: ctnetlink: fix refcount leak on table dump\n\nThere is a reference count leak in ctnetlink_dump_table():\n if (res \u003c 0) {\n nf_conntrack_get(\u0026ct-\u003ect_general); // HERE\n cb-\u003eargs[1] = (unsigned long)ct;\n ...\n\nWhile its very unlikely, its possible that ct == last.\nIf this happens, then the refcount of ct was already incremented.\nThis 2nd increment is never undone.\n\nThis prevents the conntrack object from being released, which in turn\nkeeps prevents cnet-\u003ecount from dropping back to 0.\n\nThis will then block the netns dismantle (or conntrack rmmod) as\nnf_conntrack_cleanup_net_list() will wait forever.\n\nThis can be reproduced by running conntrack_resize.sh selftest in a loop.\nIt takes ~20 minutes for me on a preemptible kernel on average before\nI see a runaway kworker spinning in nf_conntrack_cleanup_net_list.\n\nOne fix would to change this to:\n if (res \u003c 0) {\n\t\tif (ct != last)\n\t nf_conntrack_get(\u0026ct-\u003ect_general);\n\nBut this reference counting isn\u0027t needed in the first place.\nWe can just store a cookie value instead.\n\nA followup patch will do the same for ctnetlink_exp_dump_table,\nit looks to me as if this has the same problem and like\nctnetlink_dump_table, we only need a \u0027skip hint\u0027, not the actual\nobject so we can apply the same cookie strategy there as well."
}
],
"providerMetadata": {
"dateUpdated": "2025-09-04T15:33:14.891Z",
"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
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"references": [
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"url": "https://git.kernel.org/stable/c/586892e341fbf698e7cbaca293e1353957db725a"
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{
"url": "https://git.kernel.org/stable/c/962518c6ca9f9a13df099cafa429f72f68ad61f0"
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{
"url": "https://git.kernel.org/stable/c/19b909a4b1452fb97e477d2f08b97f8d04095619"
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{
"url": "https://git.kernel.org/stable/c/41462f4cfc583513833f87f9ee55d12da651a7e3"
},
{
"url": "https://git.kernel.org/stable/c/30cf811058552b8cd0e98dff677ef3f89d6d34ce"
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{
"url": "https://git.kernel.org/stable/c/a2cb4df7872de069f809de2f076ec8e54d649fe3"
},
{
"url": "https://git.kernel.org/stable/c/e14f72aa66c029db106921d621edcedef68e065b"
},
{
"url": "https://git.kernel.org/stable/c/a62d6aa3f31f216b637a4c71b7a8bfc7c57f049b"
},
{
"url": "https://git.kernel.org/stable/c/de788b2e6227462b6dcd0e07474e72c089008f74"
}
],
"title": "netfilter: ctnetlink: fix refcount leak on table dump",
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"cveId": "CVE-2025-38721",
"datePublished": "2025-09-04T15:33:14.891Z",
"dateReserved": "2025-04-16T04:51:24.033Z",
"dateUpdated": "2025-09-04T15:33:14.891Z",
"state": "PUBLISHED"
},
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"nvd": "{\"cve\":{\"id\":\"CVE-2025-38721\",\"sourceIdentifier\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"published\":\"2025-09-04T16:15:41.843\",\"lastModified\":\"2025-09-05T17:47:24.833\",\"vulnStatus\":\"Awaiting Analysis\",\"cveTags\":[],\"descriptions\":[{\"lang\":\"en\",\"value\":\"In the Linux kernel, the following vulnerability has been resolved:\\n\\nnetfilter: ctnetlink: fix refcount leak on table dump\\n\\nThere is a reference count leak in ctnetlink_dump_table():\\n if (res \u003c 0) {\\n nf_conntrack_get(\u0026ct-\u003ect_general); // HERE\\n cb-\u003eargs[1] = (unsigned long)ct;\\n ...\\n\\nWhile its very unlikely, its possible that ct == last.\\nIf this happens, then the refcount of ct was already incremented.\\nThis 2nd increment is never undone.\\n\\nThis prevents the conntrack object from being released, which in turn\\nkeeps prevents cnet-\u003ecount from dropping back to 0.\\n\\nThis will then block the netns dismantle (or conntrack rmmod) as\\nnf_conntrack_cleanup_net_list() will wait forever.\\n\\nThis can be reproduced by running conntrack_resize.sh selftest in a loop.\\nIt takes ~20 minutes for me on a preemptible kernel on average before\\nI see a runaway kworker spinning in nf_conntrack_cleanup_net_list.\\n\\nOne fix would to change this to:\\n if (res \u003c 0) {\\n\\t\\tif (ct != last)\\n\\t nf_conntrack_get(\u0026ct-\u003ect_general);\\n\\nBut this reference counting isn\u0027t needed in the first place.\\nWe can just store a cookie value instead.\\n\\nA followup patch will do the same for ctnetlink_exp_dump_table,\\nit looks to me as if this has the same problem and like\\nctnetlink_dump_table, we only need a \u0027skip hint\u0027, not the actual\\nobject so we can apply the same cookie strategy there as well.\"}],\"metrics\":{},\"references\":[{\"url\":\"https://git.kernel.org/stable/c/19b909a4b1452fb97e477d2f08b97f8d04095619\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/30cf811058552b8cd0e98dff677ef3f89d6d34ce\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/41462f4cfc583513833f87f9ee55d12da651a7e3\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/586892e341fbf698e7cbaca293e1353957db725a\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/962518c6ca9f9a13df099cafa429f72f68ad61f0\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/a2cb4df7872de069f809de2f076ec8e54d649fe3\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/a62d6aa3f31f216b637a4c71b7a8bfc7c57f049b\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/de788b2e6227462b6dcd0e07474e72c089008f74\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/e14f72aa66c029db106921d621edcedef68e065b\",\"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.
- 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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