CVE-2014-0099: Improper Neutralization of CRLF Sequences in HTTP Headers in Apache Tomcat

org.apache.tomcat:tomcat Updated 02 Oct 2025

Summary

14/05/2022

Disclosed on

CVE-2014-0099

CVE

Yes i

Fix available

Moderate

Severity

Not published

CVSS Score

CVE-2014-0099: Improper Neutralization of CRLF Sequences in HTTP Headers in Apache Tomcat. Affects org.apache.tomcat:tomcat across 3 version ranges.

< 6.0.40 >= 7.0.0, < 7.0.54 >= 8.0.0, < 8.0.6

Fixed in 6.0.40, 7.0.54 or 8.0.6, depending on the release line you run. How to fix ↓

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Background

Apache Tomcat is an open-source web server and servlet container that is widely used for hosting Java-based web applications. It provides a robust and scalable platform for running Java web applications. This vulnerability affects versions of Apache Tomcat prior to 6.0.40, 7.x prior to 7.0.53, and 8.x prior to 8.0.4. The vulnerability arises when Apache Tomcat is operated behind a reverse proxy. An attacker can exploit this vulnerability by sending a crafted Content-Length HTTP header, leading to HTTP request smuggling attacks.

Vulnerability Detail

The vulnerability (CVE-2014-0099) in Apache Tomcat allows remote attackers to conduct HTTP request smuggling attacks. The issue is caused by an integer overflow in the Ascii.java file of the Tomcat utility library. When operated behind a reverse proxy, an attacker can manipulate the Content-Length HTTP header to bypass security measures and smuggle malicious requests. This can lead to various security risks, including unauthorized access, data leakage, and potential remote code execution.

How To Fix

Fixed versions by release line

The minimum fixed version depends on the release line you run.

< 6.0.40 6.0.40
>= 7.0.0, < 7.0.54 7.0.54
>= 8.0.0, < 8.0.6 8.0.6

Tip — Not sure which release line you're on? Vulert can find the fix for the version you are using. Scan free →

Workaround

If upgrading Apache Tomcat is not immediately feasible, a possible workaround is to configure the reverse proxy to reject or sanitize requests with a crafted Content-Length HTTP header. This can be achieved by implementing custom request filtering rules or using a web application firewall (WAF) to block such requests. However, applying the workaround may introduce additional complexities and is not a substitute for upgrading to a fixed version.

Conclusion

The vulnerability (CVE-2014-0099) in Apache Tomcat allows remote attackers to conduct HTTP request smuggling attacks. It is crucial to upgrade to a fixed version of Apache Tomcat to mitigate the risk. Regularly updating Apache Tomcat and implementing security best practices are essential to protect against such vulnerabilities. For further support and assistance in vulnerability remediation, you can reach out to DevNack.com.

See every vulnerability recorded for org.apache.tomcat:tomcat →

FAQ

What is Apache Tomcat?

Apache Tomcat is an open-source web server and servlet container that provides a platform for running Java-based web applications.

What is HTTP request smuggling?

HTTP request smuggling is a technique used by attackers to manipulate the interpretation of HTTP requests by intermediaries, such as reverse proxies or web application firewalls, leading to security vulnerabilities.

What are the potential risks of this vulnerability?

The potential risks of this vulnerability include unauthorized access to sensitive information, data leakage, and potential remote code execution.

How can I check if my application is affected by this vulnerability?

You can use Vulert Playground (https://vulert.com/scanner) to check if your application is affected by this vulnerability. Vulert Playground allows you to analyze your pom.xml file and provides real-time alerts for open-source vulnerabilities.