CVE-2017-9802: Apache Sling Servlets Post - Improper Neutralization of Input During Web Page Generation

Background

The Apache Sling Servlets Post package is a component of the Apache Sling framework, which is designed to provide a web framework for building content-oriented applications. The servlets.post module specifically handles HTTP POST requests for creating or modifying content in the Apache Sling repository. It allows users to interact with the repository by submitting data through POST requests.

Vulnerability Detail

The vulnerability identified as CVE-2017-9802 affects the Apache Sling Servlets Post package. The issue arises from the improper neutralization of input during web page generation. The Javascript method Sling.evalString() in Apache Sling Servlets Post before version 2.3.22 uses the 'eval' function to parse input strings. This allows for cross-site scripting (XSS) attacks by passing specially crafted input strings. An attacker could exploit this vulnerability to inject malicious code into web pages generated by the Apache Sling Servlets Post package, potentially leading to unauthorized access, data theft, or other malicious activities.

Workaround

If upgrading to the latest version is not immediately feasible, a temporary workaround can be implemented by disabling the use of the Sling.evalString() method or by implementing input validation and sanitization techniques to prevent the execution of malicious code. Here is an example of input validation using Java code:

String input = request.getParameter("input");
if (input != null && !input.isEmpty()) {
    // Perform input validation and sanitization
    // ... your code here ...
}

By validating and sanitizing user input, the risk of XSS attacks can be mitigated.

Conclusion

The CVE-2017-9802 vulnerability in the Apache Sling Servlets Post package allows for cross-site scripting (XSS) attacks by exploiting the improper neutralization of input during web page generation. To mitigate this vulnerability, it is recommended to upgrade to Apache Sling Servlets Post version 2.3.22 or later. If immediate upgrading is not feasible, implementing input validation and sanitization techniques can provide temporary protection. For further assistance and support in vulnerability remediation, please contact DevNack.com.

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