Format String Vulnerability in Clearsilver CGI Kit Leading to Potential Denial of Service
Summary
CVE-2011-4357: Format string vulnerability in the p_cgi_error function in python/neo_cgi.c in the Python CGI Kit (neo_cgi) module for Clearsilver 0.10.5 and earlier allows remote attackers to cause a denial of service (crash) and possi... Affects clearsilver versions < 0.10.5-1.3. Fixed in 0.10.5-1.3. How to fix ↓
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Background
Clearsilver is a fast, powerful, and flexible template system used for web applications. It is designed to separate content from presentation, allowing developers to create dynamic web pages efficiently. The Python CGI Kit (neo_cgi) module is a part of Clearsilver that facilitates the creation of Common Gateway Interface (CGI) scripts. However, versions 0.10.5 and earlier are susceptible to a format string vulnerability that can be exploited by remote attackers.
Vulnerability Detail
The vulnerability arises from improper handling of format string specifiers in the p_cgi_error function within the neo_cgi.c file of the Clearsilver package. Attackers can craft malicious input that, when processed by the cgi_error API function, can lead to a denial of service by crashing the application. In some cases, it may also allow the execution of arbitrary code, posing significant security risks to affected systems.
How To Fix
Minimum fixed version
0.10.5-1.3
This is the first release that contains the fix.
sudo apt-get install --only-upgrade clearsilverTip — Not sure which version your app runs? Vulert can match this fix to it. Scan free →
Workaround
If upgrading is not immediately possible, consider disabling the CGI functionality temporarily or restricting access to the affected scripts until a patch can be applied. Additionally, validate and sanitize all user inputs to mitigate the risk of exploitation.
Conclusion
The format string vulnerability in the Clearsilver CGI Kit poses significant risks, including denial of service and potential arbitrary code execution. It is crucial for users of affected versions to upgrade to the latest version to ensure the security of their applications. Utilizing tools like Vulert can help monitor and alert for such vulnerabilities in real-time.
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FAQ
A format string vulnerability occurs when an application improperly handles user-supplied input as a format string, potentially allowing attackers to read memory or execute arbitrary code.
You can use Vulert's playground at Vulert Scanner to check if your application is affected by this vulnerability without requiring any signup.
Exploitation of this vulnerability can lead to application crashes and may allow attackers to execute arbitrary code, compromising the security of the system.
Yes, upgrading to Clearsilver version 0.10.5-1.3 or later mitigates this vulnerability.
Consider disabling CGI functionality or restricting access to affected scripts as a temporary measure until you can apply the necessary updates.
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