CVE-2025-38721

Technical 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) {

Remediation

Check the references section for vendor advisories and patches from linux. Update linux_kernel to the latest patched version. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

Affected Products

References