# CVE-2016-4993: Improper Neutralization of CRLF Sequences in Wildfly Undertow

> Remote attackers can inject HTTP headers and split responses in WildFly Undertow, potentially manipulating client interactions.

- **Severity:** Medium 6.1 (`CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** A user has to click or open something
- **Fix available:** Yes
- **Published:** 26 Sep 2016
- **Updated:** 6 Aug 2024
- **Also known as:** CVE-2016-6339, DEBIAN-CVE-2016-4993, GHSA-qcqr-hcjq-whfq, UBUNTU-CVE-2016-4993

## What is CVE-2016-4993?

CVE-2016-4993 is a medium-severity vulnerability in Redhat Jboss Enterprise Application Platform, published on 26 Sep 2016. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.

### Official description

CRLF injection vulnerability in the Undertow web server in WildFly 10.0.0, as used in Red Hat JBoss Enterprise Application Platform (EAP) 7.x before 7.0.2, allows remote attackers to inject arbitrary HTTP headers and conduct HTTP response splitting attacks via unspecified vectors.

Weakness: CWE-93 (Improper Neutralization of CRLF Sequences), CWE-113 (Improper Neutralization of CRLF Sequences in HTTP Headers)

## Which versions are affected by CVE-2016-4993?

2 open source packages ship an affected version, including org.wildfly:wildfly-undertow. It affects 2 products.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `org.wildfly:wildfly-undertow` | Maven | From 10.0.0.Final | 11.0.0.Final |
| `org.wildfly:wildfly-undertow` | Maven | From 10.0.0.Final | 11.0.0.Final |

Products: Redhat Jboss Enterprise Application Platform, Redhat Jboss Wildfly Application Server.

## How do I fix CVE-2016-4993?

Upgrade org.wildfly:wildfly-undertow to 11.0.0.Final or later.

## Is CVE-2016-4993 being exploited?

There is no known exploitation of CVE-2016-4993 in the wild and no public exploit code.

## Other vulnerabilities in Redhat Jboss Enterprise Application Platform

- [CVE-2017-12149](https://insights.sbomify.com/CVE-2017-12149/): Red Hat JBoss Application Server Remote Code Execution (critical 9.8, exploited in the wild)
- [CVE-2010-1428](https://insights.sbomify.com/CVE-2010-1428/): Red Hat JBoss Information Disclosure (medium 5.9, exploited in the wild)
- [CVE-2010-0738](https://insights.sbomify.com/CVE-2010-0738/): Red Hat JBoss Authentication Bypass (low 3.7, exploited in the wild)
- [CVE-2016-3690](https://insights.sbomify.com/CVE-2016-3690/): Deserialization in n/a (critical 9.8)
- [CVE-2017-7504](https://insights.sbomify.com/CVE-2017-7504/): Deserialization in JBoss (critical 9.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2016-4993 and fix it if it is affected.

What it is: CVE-2016-4993 is a medium-severity vulnerability in Redhat Jboss Enterprise Application Platform, published on 26 Sep 2016. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Exploitation: There is no known exploitation of CVE-2016-4993 in the wild and no public exploit code.

Affected packages and fixed versions:
- org.wildfly:wildfly-undertow (Maven): affected from 10.0.0.Final; fixed in 11.0.0.Final
- org.wildfly:wildfly-undertow (Maven): affected from 10.0.0.Final; fixed in 11.0.0.Final

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-2016-4993/ (Markdown: https://insights.sbomify.com/CVE-2016-4993/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2016-4993
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2016-4993
- OSV: https://osv.dev/vulnerability/CVE-2016-4993

---
From sbomify Insights: https://insights.sbomify.com/CVE-2016-4993/
Summaries are generated and may contain mistakes; the official description above is the record.