CVE-2026-23016

/// Technical description

In the Linux kernel, the following vulnerability has been resolved:

inet: frags: drop fraglist conntrack references

Jakub added a warning in nf_conntrack_cleanup_net_list() to make debugging

leaked skbs/conntrack references more obvious.

syzbot reports this as triggering, and I can also reproduce this via

ip_defrag.sh selftest:

conntrack cleanup blocked for 60s

WARNING: net/netfilter/nf_conntrack_core.c:2512

[..]

conntrack clenups gets stuck because there are skbs with still hold nf_conn

references via their frag_list.

net.core.skb_defer_max=0 makes the hang disappear.

Eric Dumazet points out that skb_release_head_state() doesn't follow the

fraglist.

ip_defrag.sh can only reproduce this problem since

commit 6471658dc66c ("udp: use skb_attempt_defer_free()"), but AFAICS this

problem could happen with TCP as well if pmtu discovery is off.

The relevant problem path for udp is:

1. netns emits fragmented packets

2. nf_defrag_v6_hook reassembles them (in output hook)

3. reasse

/// Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. 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.

/// References