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 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 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.

Severity MEDIUM

CVSS Score 5.5

CVSS Vector CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

CWE N/A

Public Exploit ✅ No

Source NVD

Published 2025-09-04

Updated 2026-06-02

Modified 2026-05-12

Fix URL https://git.kernel.org/stable/c/19b909a4b1452fb97e477d2f08b97f8d04095619

Software	From version	Fixed in
debian-linux	—	—
linux-kernel	—	—