CVE-2016-6816: Improper Input Validation in Apache Tomcat

org.apache.tomcat:tomcat-coyote Updated 02 Oct 2025

Summary

13/05/2022

Disclosed on

CVE-2016-6816

CVE

Yes i

Fix available

High

Severity

7.1

CVSS Score

CVE-2016-6816: Improper Input Validation in Apache Tomcat. Affects org.apache.tomcat:tomcat-coyote across 5 version ranges.

>= 6.0.0, < 6.0.48 >= 7.0.0, < 7.0.73 >= 8.0.0RC1, < 8.0.39 >= 8.5.0, < 8.5.8 >= 9.0.0.M1, < 9.0.0.M12

Fixed in 5 releases; the minimum fixed version depends 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 used to deploy Java-based web applications. It provides a Java HTTP web server environment for running Java code. The vulnerability identified as CVE-2016-6816 affects Apache Tomcat versions 9.0.0.M1 to 9.0.0.M11, 8.5.0 to 8.5.6, 8.0.0.RC1 to 8.0.38, 7.0.0 to 7.0.72, and 6.0.0 to 6.0.47. This vulnerability arises from improper input validation in the code that parses the HTTP request line. It allows for the presence of invalid characters, which can be exploited in conjunction with a proxy that also permits these invalid characters but with a different interpretation. This can lead to various attacks, including web-cache poisoning, cross-site scripting (XSS), and unauthorized access to sensitive information from requests other than the attacker's own.

Vulnerability Detail

The vulnerability in Apache Tomcat arises from the improper input validation in the code that parses the HTTP request line. This allows for the presence of invalid characters, which can be exploited in conjunction with a proxy that also permits these invalid characters but with a different interpretation. By manipulating the HTTP response, an attacker can poison a web-cache, perform cross-site scripting (XSS) attacks, and gain access to sensitive information from requests other than their own. This vulnerability has a CVSS score of 7.1, indicating a high severity level.

How To Fix

Fixed versions by release line

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

>= 6.0.0, < 6.0.48 6.0.48
>= 7.0.0, < 7.0.73 7.0.73
>= 8.0.0RC1, < 8.0.39 8.0.39
>= 8.5.0, < 8.5.8 8.5.8
>= 9.0.0.M1, < 9.0.0.M12 9.0.0.M12

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

Workaround

There is no specific workaround mentioned for this vulnerability.

Conclusion

The vulnerability in Apache Tomcat (CVE-2016-6816) arises from improper input validation in the code that parses the HTTP request line. It allows for the presence of invalid characters, which can be exploited to perform various attacks. To mitigate this vulnerability, it is recommended to upgrade to the fixed versions of Apache Tomcat. For further support on vulnerability remediation, you can contact DevNack.com.

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