Denial of Service Vulnerability in Squid Proxy Server
Summary
ALPINE-CVE-2021-31808: An issue was discovered in Squid before 4.15 and 5.x before 5.0.6. Affects squid versions < 4.15-r0. Fixed in 4.15-r0. How to fix ↓
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Background
Squid is a widely-used caching proxy for the web that supports HTTP, HTTPS, FTP, and more. It is designed to improve web performance by caching frequently requested content, reducing bandwidth usage, and enhancing response times. However, Squid is susceptible to certain vulnerabilities that can compromise its functionality and the security of the systems relying on it.
Vulnerability Detail
An issue was discovered in Squid before version 4.15 and in the 5.x series before version 5.0.6. This vulnerability arises from an input-validation bug that allows an attacker to exploit the proxy server through a crafted HTTP Range request. The result is a Denial of Service (DoS) attack, which can disrupt service for all clients utilizing the proxy. The technical implications of this vulnerability are significant, as it can lead to service outages and impact the availability of web resources for users.
How To Fix
Minimum fixed version
4.15-r0
This is the first release that contains the fix.
sudo apk add --upgrade squidTip — Not sure which version your app runs? Vulert can match this fix to it. Scan free →
Workaround
As a temporary measure, users can restrict access to the proxy server or disable HTTP Range requests until the package is updated. This can be done by modifying the Squid configuration file to deny such requests.
Conclusion
The Denial of Service vulnerability in Squid poses a significant risk to users relying on this proxy server. It is crucial to update to the latest patched versions to mitigate the risk and ensure continued service availability. Utilizing tools like Vulert can help monitor and alert for such vulnerabilities in real-time.
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FAQ
The CVSS score of this vulnerability is 6.5, indicating a medium severity level.
You can use Vulert, which monitors open-source vulnerabilities in real-time. By uploading your manifest file like package-lock.json, you can check for vulnerabilities without needing to install any software.
The primary impact is a Denial of Service attack, which can render the proxy server unavailable to clients, affecting web access and performance.
Yes, versions 4.15-r0 and 5.0.6-r0 and later are patched and safe to use.
Detailed information can be found in the CVE database or through the Alpine Linux security advisories.
References
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