Unauthenticated PHP Object Injection in Roisin

Executive Summary

CVE-2026-40754 is an unauthenticated PHP Object Injection vulnerability found in the WordPress Roisin Theme versions 1.4 and below.

This flaw allows attackers to inject malicious PHP objects without needing to log in or authenticate, potentially leading to severe security issues.

The vulnerability is classified under OWASP Top 10 A3: Injection and has a high severity with a CVSS score of 8.1.

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Impact Analysis

Exploitation of this vulnerability can lead to multiple serious impacts including remote code execution, SQL injection, path traversal, and denial of service attacks.

Attackers can leverage this flaw to execute arbitrary code or manipulate the website’s database, potentially compromising the entire system.

Because the vulnerability requires no authentication, it can be exploited by anyone, increasing the risk of mass exploitation campaigns targeting many websites.

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Detection Guidance

The vulnerability affects WordPress sites using the Roisin theme version 1.4 or below and involves unauthenticated PHP Object Injection. Detection can focus on identifying the vulnerable theme version and monitoring for suspicious requests attempting code injection or exploitation patterns.

• Check the installed Roisin theme version in your WordPress installation to confirm if it is 1.4 or below.
• Use web server logs or network monitoring tools to look for unusual HTTP requests targeting the theme, especially those containing serialized PHP objects or suspicious payloads.
• Example command to check the theme version via WP-CLI: `wp theme list --status=active` and verify the Roisin theme version.
• Example command to search web server logs for suspicious payloads: `grep -i 'O:' /var/log/apache2/access.log` (searching for PHP serialized object injection attempts).

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Mitigation Strategies

Immediate mitigation involves either updating the Roisin theme to version 1.5 or later, which contains the patch for this vulnerability, or applying a mitigation rule to block attacks until the update can be performed.

• Update the Roisin theme to version 1.5 or later as soon as possible.
• If updating immediately is not possible, apply Patchstack’s mitigation rule to block exploitation attempts targeting this vulnerability.
• Monitor your site for suspicious activity and consider temporarily disabling the Roisin theme if feasible.

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Compliance Impact

The vulnerability in the Roisin WordPress theme allows unauthenticated PHP Object Injection, which can lead to code execution, SQL injection, path traversal, and denial of service attacks.

Such exploitation risks compromising the confidentiality, integrity, and availability of data hosted on affected websites.

This can impact compliance with common standards and regulations like GDPR and HIPAA, which require protection of sensitive data and maintaining system security to prevent unauthorized access or data breaches.

Failure to mitigate this vulnerability could result in violations of these regulations due to potential data exposure or service disruption.

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