Deserialization of Untrusted Data in Themeum Kirki

Executive Summary

CVE-2026-57724 is a PHP Object Injection vulnerability found in the WordPress Kirki Plugin versions 6.0.12 and earlier. It arises from the deserialization of untrusted data, which allows attackers to inject malicious objects into the application.

This vulnerability can be exploited if a suitable POP (Property Oriented Programming) chain exists, enabling attackers to perform various malicious actions such as code injection, SQL injection, path traversal, and denial of service.

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Detection Guidance

Detecting the CVE-2026-57724 vulnerability on your network or system involves checking for the presence of the vulnerable Kirki plugin version and monitoring for signs of exploitation. Below are some methods and commands to help identify the issue.

• Check the installed version of the Kirki plugin on your WordPress site. The vulnerability affects versions up to and including 6.0.12. You can verify the version by navigating to the WordPress admin dashboard, then going to 'Plugins' and locating the Kirki plugin. The version number will be displayed there.
• Use the WordPress command-line interface (WP-CLI) to check the plugin version. Run the following command: wp plugin list --name=kirki --fields=name,version,status. This will display the installed version of the Kirki plugin.
• Inspect your web server logs for suspicious activity related to PHP object injection. Look for unusual POST requests or serialized data in HTTP requests targeting the Kirki plugin. For example, you can use grep to search for patterns like 'O:' or 'a:' in your access logs, which may indicate serialized data: grep -r 'O:[0-9]:' /var/log/apache2/ or grep -r 'a:[0-9]:' /var/log/nginx/.
• Monitor network traffic for unexpected or malicious payloads targeting the Kirki plugin. Tools like Wireshark or tcpdump can be used to capture and analyze traffic. For example, use tcpdump to capture traffic on port 80 or 443: sudo tcpdump -i eth0 -s 0 -A 'port 80 or port 443' | grep -i 'kirki'.
• Use a vulnerability scanner or security plugin like Patchstack, Wordfence, or Sucuri to scan your WordPress site for known vulnerabilities, including CVE-2026-57724. These tools can automatically detect outdated or vulnerable plugins.
• If you have access to the server's file system, manually inspect the Kirki plugin directory for any unexpected or malicious files. The plugin is typically located in the /wp-content/plugins/kirki/ directory.

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Impact Analysis

This vulnerability has a high severity score of 9.8, indicating it poses a significant risk. If exploited, attackers can execute arbitrary code, manipulate databases via SQL injection, access unauthorized files through path traversal, or cause denial of service, potentially compromising the entire website.

Such impacts can lead to data breaches, website defacement, service outages, and loss of user trust.

Immediate mitigation involves updating the Kirki plugin to version 6.0.13 or later or applying provided mitigation rules to block attacks until the update is applied.

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Compliance Impact

This vulnerability, a PHP Object Injection with a CVSS score of 9.8, can severely impact compliance with standards and regulations like GDPR and HIPAA due to its potential for unauthorized access, data breaches, and code execution.

• GDPR: The vulnerability allows attackers to execute malicious activities such as data exfiltration or manipulation. If personal data of EU citizens is compromised, organizations may face violations of GDPR's data protection principles (Article 5), fail to ensure data security (Article 32), and incur significant fines (up to 4% of global revenue or €20 million).
• HIPAA: For organizations handling protected health information (PHI), this vulnerability could lead to unauthorized access or disclosure of sensitive patient data. This violates the HIPAA Security Rule (45 CFR Part 164, Subpart C), which mandates safeguards for electronic PHI. Non-compliance may result in penalties ranging from $100 to $50,000 per violation, with annual maximums up to $1.5 million.
• Other standards: The vulnerability may also conflict with requirements in frameworks like ISO 27001 (information security management) or PCI DSS (payment card data protection), where deserialization of untrusted data is explicitly discouraged due to the risk of exploitation.

Organizations using the affected plugin must address the vulnerability immediately to avoid regulatory scrutiny, legal consequences, and reputational damage.

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Mitigation Strategies

Immediate action is required to mitigate the risk of this high-priority PHP Object Injection vulnerability in the WordPress Kirki Plugin (versions 6.0.12 and earlier).

• Update the Kirki plugin to version 6.0.13 or later.
• If updating immediately is not possible, apply the mitigation rule provided by Patchstack to block attacks until the plugin is updated.
• Seek assistance from your hosting provider or a web developer to help implement these mitigations.

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