# CVE-2026-53228: ipv6: sit: reload inner IPv6 header after GSO offloads

> A use-after-free vulnerability in the Linux kernel's IPv6 SIT tunnel allows attackers to execute code or cause a denial of service via crafted packets.

- **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:** 25 Jun 2026
- **Updated:** 19 Oct 2026
- **Also known as:** AZL-90734, BELL-CVE-2026-53228, DEBIAN-CVE-2026-53228, GHSA-5q2p-7748-g6qp, ROOT-OS-DEBIAN-11-CVE-2026-53228, ROOT-OS-DEBIAN-12-CVE-2026-53228, ROOT-OS-UBUNTU-2204-CVE-2026-53228, ROOT-OS-UBUNTU-2404-CVE-2026-53228, UBUNTU-CVE-2026-53228

## What is CVE-2026-53228?

CVE-2026-53228 is a critical use after free vulnerability in Linux kernel, published on 25 Jun 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:

ipv6: sit: reload inner IPv6 header after GSO offloads

ipip6_tunnel_xmit() caches the inner IPv6 header pointer at function
entry and continues using it after iptunnel_handle_offloads().

For GSO skbs, iptunnel_handle_offloads() calls skb_header_unclone().
When the skb header is cloned, skb_header_unclone() can call
pskb_expand_head(), which may move the skb head. The pskb_expand_head()
contract requires pointers into the skb header to be reloaded after the
call.

If the later skb_realloc_headroom() branch is not taken, SIT uses the
stale iph6 pointer to read the inner hop limit and DS field. That can
read from a freed skb head after the old head's remaining clone is
released.

Reload iph6 after the offload helper succeeds and before subsequent
reads from the inner IPv6 header. Keep the existing reload after
skb_realloc_headroom(), since that branch can also replace the skb.

Weakness: CWE-416 (Use After Free)

## Which versions are affected by CVE-2026-53228?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2026-53228?

Apply the vendor's patch.

## Is CVE-2026-53228 being exploited?

There is no known exploitation of CVE-2026-53228 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-2026-53228 and fix it if it is affected.

What it is: CVE-2026-53228 is a critical use after free vulnerability in Linux kernel, published on 25 Jun 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-2026-53228 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-2026-53228/ (Markdown: https://insights.sbomify.com/CVE-2026-53228/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-53228
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-53228
- OSV: https://osv.dev/vulnerability/CVE-2026-53228

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-53228/
Summaries are generated and may contain mistakes; the official description above is the record.