Critical NULL Pointer Dereference in Squid HTTP Caching Proxy
Summary
ALPINE-CVE-2018-1000027: The Squid Software Foundation Squid HTTP Caching Proxy version prior to version 4.0.23 contains a NULL Pointer Dereference vulnerability in HTTP Response X-Forwarded-For header processing that can result in Denial of Ser... Affects squid versions < 3.5.27-r2. Fixed in 3.5.27-r2. How to fix ↓
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Background
Squid is a widely used caching proxy for the web, supporting HTTP, HTTPS, FTP, and more. It is designed to improve web performance by caching frequently requested content and reducing bandwidth usage. However, certain versions of Squid prior to 4.0.23 are vulnerable to a NULL Pointer Dereference vulnerability, which can lead to Denial of Service (DoS) for all clients using the proxy.
Vulnerability Detail
The vulnerability arises from improper handling of the X-Forwarded-For HTTP response header. When a remote HTTP server responds with this header in certain types of requests, it can trigger a NULL Pointer Dereference, causing the Squid proxy to crash. This results in a Denial of Service, affecting all clients relying on the proxy for web access. The vulnerability has been assigned a CVSS score of 7.5, indicating a high severity level.
How To Fix
Minimum fixed version
3.5.27-r2
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, you can disable the processing of the X-Forwarded-For header by configuring your Squid settings. However, this may impact the functionality of your proxy. It is recommended to apply the patch as soon as possible instead of relying on workarounds.
Conclusion
The NULL Pointer Dereference vulnerability in Squid HTTP Caching Proxy poses a significant risk, leading to potential Denial of Service for users. It is crucial to update to the latest version to mitigate this risk effectively. Utilizing tools like Vulert can further enhance your security posture by monitoring for vulnerabilities in real-time.
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FAQ
The vulnerability can lead to a Denial of Service, causing the Squid proxy to crash and making it unavailable for all clients.
You can use the Vulert playground at Vulert Scanner to check if your application is affected by this vulnerability without needing to sign up.
All versions of Squid prior to 4.0.23 are affected by this vulnerability.
Yes, updating to version 4.0.23 or later of Squid will permanently fix the vulnerability.
Vulert monitors and alerts for open-source vulnerabilities in software using just a manifest file. It provides real-time alerts for vulnerabilities, helping developers maintain secure applications.
References
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