# GSD-2021-1001439: net: validate lwtstate->data before returning from skb_tunnel_info()

> A missing validation in the Linux kernel network stack can cause a null pointer dereference, leading to a system crash.

- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 3 Aug 2021

## What is GSD-2021-1001439?

GSD-2021-1001439 is a vulnerability in Kernel, published on 3 Aug 2021. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

net: validate lwtstate->data before returning from skb_tunnel_info()

This is an automated ID intended to aid in discovery of potential security vulnerabilities. The actual impact and attack plausibility have not yet been proven.
This ID is fixed in Linux Kernel version v4.9.277 by commit b61d327cd3cc5ea591f3bf751dd11e034f388bb5, it was introduced in version v4.3 by commit 61adedf3e3f1d3f032c5a6a299978d91eff6d555. For more details please see the references link.

## Which versions are affected by GSD-2021-1001439?

1 open source package ship an affected version, including Kernel.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `Kernel` | Linux | All versions | None |

## How do I fix GSD-2021-1001439?

No fix has been published for GSD-2021-1001439 yet. Limit exposure of the affected software until one is available.

## Is GSD-2021-1001439 being exploited?

There is no known exploitation of GSD-2021-1001439 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for GSD-2021-1001439 and fix it if it is affected.

What it is: GSD-2021-1001439 is a vulnerability in Kernel, published on 3 Aug 2021. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of GSD-2021-1001439 in the wild and no public exploit code.

Affected packages and fixed versions:
- Kernel (Linux): affected all versions; no fix listed

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/GSD-2021-1001439/ (Markdown: https://insights.sbomify.com/GSD-2021-1001439/index.md)
```

## Sources

- OSV: https://osv.dev/vulnerability/GSD-2021-1001439

---
From sbomify Insights: https://insights.sbomify.com/GSD-2021-1001439/
Summaries are generated and may contain mistakes; the official description above is the record.