# CVE-2009-3623: Null dereference in n/a

> Remote attackers can crash the Linux kernel via a NULL pointer dereference in the NFSv4 callback subsystem when handling AUTH_NULL requests.

- **Severity:** High 7.8 (`AV:N/AC:L/Au:N/C:N/I:N/A:C`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 30 Oct 2009
- **Updated:** 7 Aug 2024
- **Also known as:** GHSA-4vrg-c54f-c5m9

## What is CVE-2009-3623?

CVE-2009-3623 is a high-severity vulnerability in Linux kernel, published on 30 Oct 2009. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

The lookup_cb_cred function in fs/nfsd/nfs4callback.c in the nfsd4 subsystem in the Linux kernel before 2.6.31.2 attempts to access a credentials cache even when a client specifies the AUTH_NULL authentication flavor, which allows remote attackers to cause a denial of service (NULL pointer dereference and system crash) via an NFSv4 mount request.

Weakness: CWE-287 (Improper Authentication)

## Which versions are affected by CVE-2009-3623?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2009-3623?

No fix has been published for CVE-2009-3623 yet. Limit exposure of the affected software until one is available.

## Is CVE-2009-3623 being exploited?

There is no known exploitation of CVE-2009-3623 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-2009-3623 and fix it if it is affected.

What it is: CVE-2009-3623 is a high-severity vulnerability in Linux kernel, published on 30 Oct 2009. 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-2009-3623 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-2009-3623/ (Markdown: https://insights.sbomify.com/CVE-2009-3623/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2009-3623
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2009-3623
- OSV: https://osv.dev/vulnerability/CVE-2009-3623

---
From sbomify Insights: https://insights.sbomify.com/CVE-2009-3623/
Summaries are generated and may contain mistakes; the official description above is the record.