Vulnerability in Kernel (CVE-2026-23016)

Summary

Vulnerability in Kernel (CVE-2026-23016). Risk of unauthorized operations or information disclosure. Mitigation: upgrade to 6.18.6 or later.

Original description

The description as published by the source.

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:

netns emits fragmented packets
nf_defrag_v6_hook reassembles them (in output hook)
reassembled skb is tracked (skb owns nf_conn reference)
ip6_output refragments
refragmented packets also own nf_conn reference (ip6_fragment
calls ip6_copy_metadata())
on input path, nf_defrag_v6_hook skips defragmentation: the
fragments already have skb->nf_conn attached
skbs are reassembled via ipv6_frag_rcv()
skb_consume_udp -> skb_attempt_defer_free() -> skb ends up
in pcpu freelist, but still has nf_conn reference.

Possible solutions:
1 let defrag engine drop nf_conn ent…

Source: OSV.dev (Open Source Vulnerabilities) NVD OSV

Auto-generated summary

Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.

A vulnerability tracked as CVE-2026-23016 has been found in Kernel.
Risk of unauthorized operations or information disclosure.
What to do: upgrade Kernel to 6.18.6 or later.
If unsure, ask your IT team or search "Kernel CVE-2026-23016" on the vendor's site.

CVE-2026-23016 (Kernel)
Patched: 6.18.6 — apply immediately
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.

❓ What is the problem

A vulnerability (unclassified) exists in Kernel.

📍 Affected scope

Check the vendor advisory for the affected versions of Kernel.

🔥 Severity

Severity: ?. Risk of unauthorized operations or information disclosure.

🔧 How to fix

Update to 6.18.6.

🛡️ Workaround

Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.

🔍 Detection

Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Run grep -r 'Kernel' . against your dependency files (package-lock.json, requirements.txt, go.sum) to find affected services.

Response actions

Concrete steps and command examples for SOC/SRE teams to execute in order

1
Identify exposure identify
```
grep -r 'Kernel' . | grep -v node_modules
```
リポジトリと本番環境の依存ファイル (package-lock.json / requirements.txt / go.sum / Gemfile.lock 等) で Kernel を grep し、稼働しているサービス・バージョンを把握する。
2
Apply patch patch
```
Upgrade Kernel to 6.18.6
```
ステージング環境で 6.18.6 に上げて回帰テスト → 本番反映。回帰テストはアプリの主要ハッピーパスを含めること。
3
Post-deployment verification verify
```
Confirm patched version is live in production
```
パッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。

Affected packages

Linux Kernel

[{"type":"ECOSYSTEM","events":[{"introduced":"6.18.0"},{"fixed":"6.18.6"}]}]

Fix status by distribution

Fixed packages published by each distribution for this CVE

BellSoft Alpaquita BELL-CVE-2026-23016 linux-lts Fixed in: 6.18.35-r1
Debian DEBIAN-CVE-2026-23016 linux Fixed in: 6.18.8-1