# CVE-2016-4979: Auth bypass in n/a

> Remote attackers can bypass SSL client certificate authentication in Apache HTTP Server when HTTP/2 and SSL are enabled.

- **Severity:** High 7.5 (`CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 6 Jul 2016
- **Updated:** 6 Aug 2024
- **Also known as:** DEBIAN-CVE-2016-4979, GHSA-r48c-7gpg-9q4x

## What is CVE-2016-4979?

CVE-2016-4979 is a high-severity authentication bypass vulnerability in Apache Http Server, published on 6 Jul 2016. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

The Apache HTTP Server 2.4.18 through 2.4.20, when mod_http2 and mod_ssl are enabled, does not properly recognize the "SSLVerifyClient require" directive for HTTP/2 request authorization, which allows remote attackers to bypass intended access restrictions by leveraging the ability to send multiple requests over a single connection and aborting a renegotiation.

Weakness: CWE-284 (Improper Access Control)

## Which versions are affected by CVE-2016-4979?

It affects 1 product.


Products: Apache Http Server.

## How do I fix CVE-2016-4979?

Upgrade to a fixed version.

## Is CVE-2016-4979 being exploited?

There is no known exploitation of CVE-2016-4979 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-2016-4979 and fix it if it is affected.

What it is: CVE-2016-4979 is a high-severity authentication bypass vulnerability in Apache Http Server, published on 6 Jul 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-2016-4979 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-2016-4979/ (Markdown: https://insights.sbomify.com/CVE-2016-4979/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2016-4979
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2016-4979
- OSV: https://osv.dev/vulnerability/CVE-2016-4979

---
From sbomify Insights: https://insights.sbomify.com/CVE-2016-4979/
Summaries are generated and may contain mistakes; the official description above is the record.