# CVE-2016-6866: Null dereference in n/a

> Attackers can bypass the slock screen lock and cause a crash by triggering a NULL pointer dereference with an invalid password hash.

- **Severity:** High 7.5 (`CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/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 Feb 2017
- **Updated:** 6 Aug 2024
- **Also known as:** DEBIAN-CVE-2016-6866, DLA-598-1, GHSA-h53p-2gg5-7vfm, MGASA-2016-0308, UBUNTU-CVE-2016-6866

## What is CVE-2016-6866?

CVE-2016-6866 is a high-severity vulnerability in Fedoraproject Fedora, published on 15 Feb 2017. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

slock allows attackers to bypass the screen lock via vectors involving an invalid password hash, which triggers a NULL pointer dereference and crash.

Weakness: CWE-476 (NULL Pointer Dereference)

## Which versions are affected by CVE-2016-6866?

It affects 2 products.


Products: Fedoraproject Fedora, Suckless Slock.

## How do I fix CVE-2016-6866?

Apply the vendor's patch.

## Is CVE-2016-6866 being exploited?

There is no known exploitation of CVE-2016-6866 in the wild and no public exploit code.

## Other vulnerabilities in Fedoraproject Fedora

- [CVE-2024-4577](https://insights.sbomify.com/CVE-2024-4577/): PHP-CGI OS Command Injection (critical 9.8, exploited in the wild)
- [CVE-2021-39226](https://insights.sbomify.com/CVE-2021-39226/): Grafana Authentication Bypass (critical 9.8, exploited in the wild)
- [CVE-2019-5544](https://insights.sbomify.com/CVE-2019-5544/): VMware ESXi and Horizon DaaS OpenSLP Heap-Based Buffer Overflow (critical 9.8, exploited in the wild)
- [CVE-2024-4947](https://insights.sbomify.com/CVE-2024-4947/): Google Chromium V8 Type Confusion (critical 9.6, exploited in the wild)
- [CVE-2024-4671](https://insights.sbomify.com/CVE-2024-4671/): Google Chromium Visuals Use-After-Free (critical 9.6, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2016-6866 and fix it if it is affected.

What it is: CVE-2016-6866 is a high-severity vulnerability in Fedoraproject Fedora, published on 15 Feb 2017. 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-2016-6866 in the wild and no public exploit code.

Affected product: Fedoraproject Fedora. 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-2016-6866/ (Markdown: https://insights.sbomify.com/CVE-2016-6866/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2016-6866
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2016-6866
- OSV: https://osv.dev/vulnerability/CVE-2016-6866

---
From sbomify Insights: https://insights.sbomify.com/CVE-2016-6866/
Summaries are generated and may contain mistakes; the official description above is the record.