HTTP Request Smuggling Vulnerability in Ruby WEBrick
Summary
DEBIAN-CVE-2025-6442: Ruby WEBrick read_header HTTP Request Smuggling Vulnerability. Affects ruby-webrick versions < 1.9.1-1. Fixed in 1.9.1-1. How to fix ↓
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Background
Ruby WEBrick is a simple HTTP server toolkit that is part of the Ruby standard library. It is used for developing and testing web applications, providing a lightweight server environment. Despite its utility, WEBrick has been found to have vulnerabilities that can be exploited, particularly when deployed behind certain HTTP proxies.
Vulnerability Detail
The Ruby WEBrick read_header HTTP Request Smuggling Vulnerability allows remote attackers to smuggle arbitrary HTTP requests on affected installations. This vulnerability arises from inconsistent parsing of terminators in HTTP headers within the read_headers method. If exploited, attackers can send malicious requests that may bypass security measures, leading to unauthorized actions or data exposure.
How To Fix
Minimum fixed version
1.9.1-1
This is the first release that contains the fix.
sudo apt-get install --only-upgrade ruby-webrickTip — Not sure which version your app runs? Vulert can match this fix to it. Scan free →
Workaround
If immediate patching is not possible, consider implementing a web application firewall (WAF) to filter and monitor HTTP requests, or configure the HTTP proxy to reject malformed requests.
Conclusion
The Ruby WEBrick HTTP Request Smuggling Vulnerability poses significant risks to applications using this toolkit. It is crucial to update to the patched version to mitigate these risks. Additionally, employing workarounds can provide temporary relief until the update is applied.
See every vulnerability recorded for ruby-webrick →
FAQ
It is an HTTP Request Smuggling vulnerability that allows attackers to send arbitrary HTTP requests.
You can check if your application is affected by using the Vulert playground at Vulert Scanner without any signup.
Exploitation can lead to unauthorized access, data exposure, or manipulation of requests, compromising the integrity of the application.
Yes, the patched version of Ruby WEBrick is 1.9.1-1 for both Debian 13 and 14.
Consider using a web application firewall to filter requests or configure your HTTP proxy to reject malformed requests as a temporary measure.
References
Related vulnerabilities
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