# CVE-2016-2161: Denial of service in Apache HTTP Server

> Malicious input to mod_auth_digest causes Apache HTTP Server to crash persistently, leading to denial of service.

- **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:** 27 Jul 2017
- **Updated:** 16 Sep 2024
- **Also known as:** DEBIAN-CVE-2016-2161, GHSA-3v6f-955w-932h, UBUNTU-CVE-2016-2161

## What is CVE-2016-2161?

CVE-2016-2161 is a high-severity denial of service vulnerability in Apache Http Server, published on 27 Jul 2017. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

In Apache HTTP Server versions 2.4.0 to 2.4.23, malicious input to mod_auth_digest can cause the server to crash, and each instance continues to crash even for subsequently valid requests.

Weakness: CWE-20 (Improper Input Validation), CWE-823 (Use of Out-of-range Pointer Offset)

## Which versions are affected by CVE-2016-2161?

It affects 1 product.


Products: Apache Http Server.

## How do I fix CVE-2016-2161?

Upgrade to a fixed version.

## Is CVE-2016-2161 being exploited?

There is no known exploitation of CVE-2016-2161 in the wild and no public exploit code.

## Other vulnerabilities in Apache Http Server

- [CVE-2021-42013](https://insights.sbomify.com/CVE-2021-42013/): Apache HTTP Server Path Traversal (critical 9.8, exploited in the wild)
- [CVE-2024-38475](https://insights.sbomify.com/CVE-2024-38475/): Apache HTTP Server Improper Escaping of Output (critical 9.1, exploited in the wild)
- [CVE-2021-40438](https://insights.sbomify.com/CVE-2021-40438/): Apache HTTP Server-Side Request Forgery (SSRF) (critical 9.0, exploited in the wild)
- [CVE-2019-0211](https://insights.sbomify.com/CVE-2019-0211/): Apache HTTP Server Privilege Escalation (high 7.8, exploited in the wild)
- [CVE-2021-41773](https://insights.sbomify.com/CVE-2021-41773/): Apache HTTP Server Path Traversal (high 7.5, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2016-2161 and fix it if it is affected.

What it is: CVE-2016-2161 is a high-severity denial of service vulnerability in Apache Http Server, published on 27 Jul 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-2016-2161 in the wild and no public exploit code.

Affected product: Apache Http Server. 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-2016-2161/ (Markdown: https://insights.sbomify.com/CVE-2016-2161/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2016-2161
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2016-2161
- OSV: https://osv.dev/vulnerability/CVE-2016-2161

---
From sbomify Insights: https://insights.sbomify.com/CVE-2016-2161/
Summaries are generated and may contain mistakes; the official description above is the record.