# CVE-2026-72442: netfilter: flowtable: fix and simplify IP6IP6 tunnel handling

> A missing header pull in Linux kernel netfilter flowtable IP6IP6 tunnel handling can cause a null pointer dereference, leading to a denial of service.

- **Severity:** Critical 9.8 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 15 Aug 2026
- **Updated:** 17 Aug 2026
- **Also known as:** DEBIAN-CVE-2026-72442, GHSA-wphh-fr34-rp9q, UBUNTU-CVE-2026-72442

## What is CVE-2026-72442?

CVE-2026-72442 is a critical vulnerability in Linux, published on 15 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

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

netfilter: flowtable: fix and simplify IP6IP6 tunnel handling

Fix nf_flow_ip6_tunnel_proto() to use pskb_may_pull() instead of
skb_header_pointer() to ensure the outer IPv6 header is in the skb
headroom, which is required for subsequent packet processing. Move
ctx->offset update inside the IPPROTO_IPV6 conditional block since it
should only be adjusted when an IP6IP6 tunnel is actually detected.
Simplify the rx path by removing ipv6_skip_exthdr() and checking
ip6h->nexthdr directly, as the flowtable fast path only handles simple
IP6IP6 encapsulation without extension headers.
Drop the tunnel encapsulation limit destination option support from the
tx path to match, since the rx path no longer handles extension headers.
Remove the encap_limit parameter from nf_flow_offload_ipv6_forward(),
nf_flow_tunnel_ip6ip6_push() and nf_flow_tunnel_v6_push(), along with
the ipv6_tel_txoption struct and related headroom/MTU adjustments.

## Which versions are affected by CVE-2026-72442?


## How do I fix CVE-2026-72442?

Apply the vendor's patch.

## Is CVE-2026-72442 being exploited?

There is no known exploitation of CVE-2026-72442 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-72442 and fix it if it is affected.

What it is: CVE-2026-72442 is a critical vulnerability in Linux, published on 15 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-72442 in the wild and no public exploit code.

Affected product: Linux. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-72442/ (Markdown: https://insights.sbomify.com/CVE-2026-72442/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-72442
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-72442
- OSV: https://osv.dev/vulnerability/CVE-2026-72442

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-72442/
Summaries are generated and may contain mistakes; the official description above is the record.