# CVE-2016-8740: Denial of service in Apache HTTP Server

> Remote attackers can cause denial of service via memory consumption in Apache HTTP Server when HTTP/2 protocols are enabled.

- **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:** 5 Dec 2016
- **Updated:** 6 Aug 2024
- **Also known as:** DEBIAN-CVE-2016-8740, GHSA-pfj2-72r3-p693, SUSE-SU-2017:0203-1

## What is CVE-2016-8740?

CVE-2016-8740 is a high-severity denial of service vulnerability in Apache Http Server, published on 5 Dec 2016. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

The mod_http2 module in the Apache HTTP Server 2.4.17 through 2.4.23, when the Protocols configuration includes h2 or h2c, does not restrict request-header length, which allows remote attackers to cause a denial of service (memory consumption) via crafted CONTINUATION frames in an HTTP/2 request.

Weakness: CWE-399, CWE-20 (Improper Input Validation)

## Which versions are affected by CVE-2016-8740?

It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `apache2` | SUSE:Linux Enterprise Server 12 SP2 | All versions | 2.4.23-16.3 |
| `apache2` | SUSE:Linux Enterprise Server for Raspberry Pi 12 SP2 | All versions | 2.4.23-16.3 |
| `apache2` | SUSE:Linux Enterprise Server for SAP Applications 12 SP2 | All versions | 2.4.23-16.3 |
| `apache2` | SUSE:Linux Enterprise Software Development Kit 12 SP2 | All versions | 2.4.23-16.3 |

Products: Apache Http Server.

## How do I fix CVE-2016-8740?

Upgrade to a fixed version.

## Is CVE-2016-8740 being exploited?

There is no known exploitation of CVE-2016-8740 in the wild and no public exploit code.

Public exploit code:

- Apache HTTP Server 2.4.23 vulnerability study (CVE-2016-8740) (github_poc): https://github.com/lcfpadilha/mac0352-ep4
- An implementation of CVE-2016-8740 (github_poc): https://github.com/jptr218/apachedos
- Apache 2.4.23 mod_http2 - Denial of Service (exploitdb)

## 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-2016-8740 and fix it if it is affected.

What it is: CVE-2016-8740 is a high-severity denial of service vulnerability in Apache Http Server, published on 5 Dec 2016. 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-2016-8740 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-2016-8740/ (Markdown: https://insights.sbomify.com/CVE-2016-8740/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2016-8740
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2016-8740
- OSV: https://osv.dev/vulnerability/CVE-2016-8740

---
From sbomify Insights: https://insights.sbomify.com/CVE-2016-8740/
Summaries are generated and may contain mistakes; the official description above is the record.