# CVE-2025-22021: netfilter: socket: Lookup orig tuple for IPv6 SNAT

> Missing conntrack lookup in IPv6 SNAT causes transparent socket matching failures, potentially bypassing network policies in Kubernetes environments.

- **Severity:** Critical 10.0 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/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:** 16 Apr 2025
- **Updated:** 15 Oct 2026
- **Also known as:** DEBIAN-CVE-2025-22021, GHSA-57hq-w56x-2gq6, ROOT-OS-DEBIAN-12-CVE-2025-22021, ROOT-OS-UBUNTU-2404-CVE-2025-22021, UBUNTU-CVE-2025-22021

## What is CVE-2025-22021?

CVE-2025-22021 is a critical vulnerability in Linux kernel, published on 16 Apr 2025. 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: socket: Lookup orig tuple for IPv6 SNAT

nf_sk_lookup_slow_v4 does the conntrack lookup for IPv4 packets to
restore the original 5-tuple in case of SNAT, to be able to find the
right socket (if any). Then socket_match() can correctly check whether
the socket was transparent.

However, the IPv6 counterpart (nf_sk_lookup_slow_v6) lacks this
conntrack lookup, making xt_socket fail to match on the socket when the
packet was SNATed. Add the same logic to nf_sk_lookup_slow_v6.

IPv6 SNAT is used in Kubernetes clusters for pod-to-world packets, as
pods' addresses are in the fd00::/8 ULA subnet and need to be replaced
with the node's external address. Cilium leverages Envoy to enforce L7
policies, and Envoy uses transparent sockets. Cilium inserts an iptables
prerouting rule that matches on `-m socket --transparent` and redirects
the packets to localhost, but it fails to match SNATed IPv6 packets due
to that missing conntrack lookup.

## Which versions are affected by CVE-2025-22021?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2025-22021?

Apply the vendor's patch.

## Is CVE-2025-22021 being exploited?

There is no known exploitation of CVE-2025-22021 in the wild and no public exploit code.

## Other vulnerabilities in Linux kernel

- [CVE-2026-53266](https://insights.sbomify.com/CVE-2026-53266/): Linux Kernel Out-of-Bounds Write (high 8.8, exploited in the wild)
- [CVE-2013-6282](https://insights.sbomify.com/CVE-2013-6282/): Linux Kernel Improper Input Validation (high 8.8, exploited in the wild)
- [CVE-2022-0185](https://insights.sbomify.com/CVE-2022-0185/): Linux Kernel Heap-Based Buffer Overflow (high 8.4, exploited in the wild)
- [CVE-2013-2094](https://insights.sbomify.com/CVE-2013-2094/): Linux Kernel Privilege Escalation (high 8.4, exploited in the wild)
- [CVE-2026-53362](https://insights.sbomify.com/CVE-2026-53362/): Linux Kernel Unspecified (high 7.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2025-22021 and fix it if it is affected.

What it is: CVE-2025-22021 is a critical vulnerability in Linux kernel, published on 16 Apr 2025. 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-2025-22021 in the wild and no public exploit code.

Affected product: Linux kernel. 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-2025-22021/ (Markdown: https://insights.sbomify.com/CVE-2025-22021/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-22021
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-22021
- OSV: https://osv.dev/vulnerability/CVE-2025-22021

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-22021/
Summaries are generated and may contain mistakes; the official description above is the record.