# CVE-2016-0736: Weak cryptography in Apache HTTP Server

> Apache HTTP Server's mod_session_crypto used unauthenticated encryption modes, allowing attackers to decrypt session data via padding oracle attacks.

- **Severity:** High 7.5 (`CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/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:** 27 Jul 2017
- **Updated:** 16 Sep 2024
- **Also known as:** DEBIAN-CVE-2016-0736, GHSA-mxm5-vg5c-rx7v, UBUNTU-CVE-2016-0736

## What is CVE-2016-0736?

CVE-2016-0736 is a high-severity 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, mod_session_crypto was encrypting its data/cookie using the configured ciphers with possibly either CBC or ECB modes of operation (AES256-CBC by default), hence no selectable or builtin authenticated encryption. This made it vulnerable to padding oracle attacks, particularly with CBC.

Weakness: CWE-310

## Which versions are affected by CVE-2016-0736?

It affects 1 product.


Products: Apache Http Server.

## How do I fix CVE-2016-0736?

Upgrade to a fixed version.

## Is CVE-2016-0736 being exploited?

There is no known exploitation of CVE-2016-0736 in the wild and no public exploit code.

Public exploit code:

- Apache mod_session_crypto - Padding Oracle (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-2016-0736 and fix it if it is affected.

What it is: CVE-2016-0736 is a high-severity 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-2016-0736 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-2016-0736/ (Markdown: https://insights.sbomify.com/CVE-2016-0736/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2016-0736
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2016-0736
- OSV: https://osv.dev/vulnerability/CVE-2016-0736

---
From sbomify Insights: https://insights.sbomify.com/CVE-2016-0736/
Summaries are generated and may contain mistakes; the official description above is the record.