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CVE-2021-36766 Explained : Impact and Mitigation

Learn about CVE-2021-36766, a critical deserialization vulnerability in Concrete5 up to version 8.5.5. Understand the impact, technical details, affected systems, and mitigation steps.

Concrete5 through 8.5.5 is affected by a deserialization vulnerability that allows malicious users to inject arbitrary PHP objects into the application scope, potentially leading to the execution of arbitrary PHP code. The vulnerable code is present in the Logging::update_logging() method within the controllers/single_page/dashboard/system/environment/logging.php file.

Understanding CVE-2021-36766

This section provides key details about the CVE-2021-36766 vulnerability.

What is CVE-2021-36766?

CVE-2021-36766 is a deserialization vulnerability in Concrete5 through version 8.5.5. It arises due to unsanitized user input passed through the logFile request parameter, leading to potential PHP Object Injection via the phar:// stream wrapper.

The Impact of CVE-2021-36766

This vulnerability could be exploited by malicious actors to inject arbitrary PHP objects into the application context, enabling them to perform various attacks, including executing unauthorized PHP code.

Technical Details of CVE-2021-36766

In this section, we delve into the technical aspects of CVE-2021-36766.

Vulnerability Description

The vulnerability resides in the inadequate sanitization of user input within the Logging::update_logging() method, allowing for PHP Object Injection via the phar:// stream wrapper.

Affected Systems and Versions

Concrete5 versions up to 8.5.5 are affected by this vulnerability.

Exploitation Mechanism

Malicious users can exploit this issue by injecting malicious PHP objects through the logFile request parameter, potentially executing unauthorized PHP code.

Mitigation and Prevention

To safeguard systems from CVE-2021-36766, immediate mitigation steps should be taken.

Immediate Steps to Take

        Upgrade Concrete5 to a version beyond 8.5.5 to mitigate the vulnerability.
        Validate and sanitize user input to prevent arbitrary PHP object injections.

Long-Term Security Practices

Implement strict input validation and output encoding practices across the application to enhance security.

Patching and Updates

Regularly apply security patches and updates provided by Concrete5 to address known vulnerabilities and improve system security.

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