CVE-2025-38721 Affecting kernel-rt-64k-devel package, versions *


Severity

Recommended
0.0
medium
0
10

Based on CentOS security rating.

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  • Snyk IDSNYK-CENTOS10-KERNELRT64KDEVEL-12489558
  • published5 Sept 2025
  • disclosed4 Sept 2025

Introduced: 4 Sep 2025

NewCVE-2025-38721  (opens in a new tab)

How to fix?

There is no fixed version for Centos:10 kernel-rt-64k-devel.

NVD Description

Note: Versions mentioned in the description apply only to the upstream kernel-rt-64k-devel package and not the kernel-rt-64k-devel package as distributed by Centos. See How to fix? for Centos:10 relevant fixed versions and status.

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.

CVSS Base Scores

version 3.1