Denial of Service and Data Exposure Vulnerability in Expat Package
Summary
DEBIAN-CVE-2013-0340: expat 2.1.0 and earlier does not properly handle entities expansion unless an application developer uses the XML_SetEntityDeclHandler function, which allows remote attackers to cause a denial of service (resource consump... Affects expat versions < 2.4.1-2. Fixed in 2.4.1-2. How to fix ↓
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Background
Expat is a widely used XML parsing library that allows applications to read and manipulate XML data efficiently. It is known for its speed and simplicity, making it a popular choice among developers for handling XML documents. However, certain versions of Expat, specifically 2.1.0 and earlier, have a vulnerability that can be exploited if developers do not implement proper entity declaration handling in their applications.
Vulnerability Detail
The vulnerability, identified as DEBIAN-CVE-2013-0340, arises from Expat's improper handling of entity expansion in XML documents. If an application does not use the XML_SetEntityDeclHandler function, it can lead to a denial of service through resource consumption, unauthorized HTTP requests to intranet servers, or even reading arbitrary files. This issue is classified as an XML External Entity (XXE) vulnerability, which poses significant risks to applications that process untrusted XML input.
How To Fix
Minimum fixed version
2.4.1-2
This is the first release that contains the fix.
sudo apt-get install --only-upgrade expatTip — Not sure which version your app runs? Vulert can match this fix to it. Scan free →
Workaround
As a temporary workaround, developers can disable external entity expansion in their applications by ensuring that they implement the XML_SetEntityDeclHandler function correctly. This will prevent the exploitation of the vulnerability until an update can be applied.
Conclusion
The vulnerability in the Expat package poses significant risks to applications that process XML data. By understanding the nature of the vulnerability and taking the necessary steps to update the package, developers can protect their applications from potential exploitation. Utilizing tools like Vulert can further enhance security by providing real-time monitoring for vulnerabilities.
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FAQ
The vulnerability allows for denial of service and potential data exposure due to improper handling of entity expansion in XML documents.
Expat versions 2.1.0 and earlier are affected by this vulnerability.
You can use the Vulert playground at Vulert Scanner to check if your application is affected by this vulnerability without requiring any signup.
You should update the Expat package to version 2.4.1-2 or later to mitigate this vulnerability.
Vulert monitors and alerts for open-source vulnerabilities in software using just a manifest file like package-lock.json, providing real-time insights into potential risks.
References
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