CVE-2019-16869: HTTP Request Smuggling in Netty
Summary
CVE-2019-16869: HTTP Request Smuggling in Netty. Affects io.netty:netty-all versions >= 4.0.0.Alpha1, < 4.1.42.Final. Fixed in 4.1.42.Final. How to fix ↓
Also tracked for
- netty · Debian:11
The same CVE-2019-16869 is tracked separately for each ecosystem and vendor. Its fix information is the same; the package and affected versions differ.
Check if this vulnerability affects your application
Upload a manifest or SBOM and we'll show whether you're affected, plus every other risky package in the same scan.
No signup required · Results in about 60 seconds
Background
Netty is a popular open-source networking framework for building high-performance, scalable applications. It provides an asynchronous event-driven architecture that allows developers to easily create network servers and clients. Netty is widely used in various applications, including web servers, proxy servers, and messaging systems. However, a vulnerability has been discovered in Netty versions before 4.1.42.Final that mishandles whitespace before the colon in HTTP headers. This vulnerability can lead to HTTP request smuggling, potentially allowing an attacker to bypass security measures and perform unauthorized actions.
Vulnerability Detail
The vulnerability in Netty arises from its mishandling of whitespace before the colon in HTTP headers. By exploiting this issue, an attacker can manipulate the headers in a way that allows them to smuggle malicious requests through the affected server. This can lead to various security risks, including bypassing authentication mechanisms, injecting malicious content, and performing unauthorized actions on behalf of other users. The vulnerability has a CVSS score of 7.5, indicating a high severity level.
How To Fix
Latest published version: 5.0.0.Alpha2 as of 22 Oct 2026
Upgrading to it may include breaking changes; the version below is the minimum fixed release for this vulnerability.
If you need the minimum change
4.1.42.Final
This is the first release that contains the fix.
Tip — Not sure which version your app runs? Vulert can match this fix to it. Scan free →
Workaround
If upgrading Netty is not immediately feasible, a temporary workaround can be implemented by manually validating and sanitizing HTTP headers before processing them. This can involve removing any leading or trailing whitespace and ensuring that the headers conform to the expected format. However, this workaround may not provide complete protection and should only be considered as a temporary measure until the Netty upgrade can be performed.
Conclusion
The vulnerability in Netty versions before 4.1.42.Final can lead to HTTP request smuggling, posing significant security risks. To mitigate this vulnerability, it is recommended to upgrade Netty to the latest patched version. If immediate upgrade is not feasible, implementing a temporary workaround and regularly monitoring for security updates can provide interim protection. For further assistance and support in vulnerability remediation, please contact DevNack.com.
See every vulnerability recorded for io.netty:netty-all →
FAQ
Netty is an open-source networking framework used for building high-performance, scalable applications. It provides an asynchronous event-driven architecture and is widely used in various applications, including web servers and proxy servers.
HTTP request smuggling is a technique used by attackers to manipulate the interpretation of HTTP requests by a server. By exploiting vulnerabilities in the server's handling of HTTP headers, an attacker can smuggle malicious requests that bypass security measures and perform unauthorized actions.
The vulnerability in Netty can lead to various security risks, including bypassing authentication mechanisms, injecting malicious content, and performing unauthorized actions on behalf of other users. It is important to promptly address this vulnerability to mitigate these risks.
You can use Vulert, a tool that monitors and alerts in real-time for open-source vulnerabilities, to check if your application is affected. Visit the Vulert Playground at Vulert Scanner and enter your application's pom.xml file to receive instant vulnerability assessment.
The CVSS score of this vulnerability is 7.5, indicating a high severity level. It is crucial to address this vulnerability promptly to protect your application and its users from potential exploitation.
