{"id":"CVE-2025-38721","title":"netfilter: ctnetlink: fix refcount leak on table dump","summary":"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 < 0) {\n                nf_conntrack_get(…","severity":"none","vendor":"Linux","product":"Linux","affected":["Linux >= d205dc40798d97d63ad348bfaf7394f445d152d4 < 586892e341fbf698e7cbaca293e1353957db725a","Linux >= d205dc40798d97d63ad348bfaf7394f445d152d4 < 962518c6ca9f9a13df099cafa429f72f68ad61f0","Linux >= d205dc40798d97d63ad348bfaf7394f445d152d4 < 19b909a4b1452fb97e477d2f08b97f8d04095619","Linux >= d205dc40798d97d63ad348bfaf7394f445d152d4 < 41462f4cfc583513833f87f9ee55d12da651a7e3","Linux >= d205dc40798d97d63ad348bfaf7394f445d152d4 < 30cf811058552b8cd0e98dff677ef3f89d6d34ce","Linux >= d205dc40798d97d63ad348bfaf7394f445d152d4 < a2cb4df7872de069f809de2f076ec8e54d649fe3","Linux >= d205dc40798d97d63ad348bfaf7394f445d152d4 < e14f72aa66c029db106921d621edcedef68e065b","Linux >= d205dc40798d97d63ad348bfaf7394f445d152d4 < a62d6aa3f31f216b637a4c71b7a8bfc7c57f049b","Linux >= d205dc40798d97d63ad348bfaf7394f445d152d4 < de788b2e6227462b6dcd0e07474e72c089008f74","Linux 2.6.18"],"published":"2025-09-04","updated":"2026-09-08","sourceUpdated":"2026-09-08T08:41:58.463Z","source":"CVEORG","sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2025-38721","references":[{"url":"https://git.kernel.org/stable/c/586892e341fbf698e7cbaca293e1353957db725a"},{"url":"https://git.kernel.org/stable/c/962518c6ca9f9a13df099cafa429f72f68ad61f0"},{"url":"https://git.kernel.org/stable/c/19b909a4b1452fb97e477d2f08b97f8d04095619"},{"url":"https://git.kernel.org/stable/c/41462f4cfc583513833f87f9ee55d12da651a7e3"},{"url":"https://git.kernel.org/stable/c/30cf811058552b8cd0e98dff677ef3f89d6d34ce"},{"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"}],"tags":["cve.org"],"epss":0.00169,"epssPercentile":0.05433,"ingestedAt":"2026-09-08T15:33:26.997Z","slug":"CVE-2025-38721","body":"## Overview\n\nIn 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 < 0) {\n                nf_conntrack_get(&ct->ct_general); // HERE\n                cb->args[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->count 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 < 0) {\n\t\tif (ct != last)\n\t                nf_conntrack_get(&ct->ct_general);\n\nBut this reference counting isn't 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 'skip hint', not the actual\nobject so we can apply the same cookie strategy there as well.\n\n## Affected\n\n- `Linux >= d205dc40798d97d63ad348bfaf7394f445d152d4 < 586892e341fbf698e7cbaca293e1353957db725a`\n- `Linux >= d205dc40798d97d63ad348bfaf7394f445d152d4 < 962518c6ca9f9a13df099cafa429f72f68ad61f0`\n- `Linux >= d205dc40798d97d63ad348bfaf7394f445d152d4 < 19b909a4b1452fb97e477d2f08b97f8d04095619`\n- `Linux >= d205dc40798d97d63ad348bfaf7394f445d152d4 < 41462f4cfc583513833f87f9ee55d12da651a7e3`\n- `Linux >= d205dc40798d97d63ad348bfaf7394f445d152d4 < 30cf811058552b8cd0e98dff677ef3f89d6d34ce`\n- `Linux >= d205dc40798d97d63ad348bfaf7394f445d152d4 < a2cb4df7872de069f809de2f076ec8e54d649fe3`\n- `Linux >= d205dc40798d97d63ad348bfaf7394f445d152d4 < e14f72aa66c029db106921d621edcedef68e065b`\n- `Linux >= d205dc40798d97d63ad348bfaf7394f445d152d4 < a62d6aa3f31f216b637a4c71b7a8bfc7c57f049b`\n- `Linux >= d205dc40798d97d63ad348bfaf7394f445d152d4 < de788b2e6227462b6dcd0e07474e72c089008f74`\n- `Linux 2.6.18`\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.","depth":"sunlit","depthScore":3,"depthScoreParts":{"impact":2.8,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[]}