Critical PHP Security Vulnerabilities: Is Your Concrete CMS Website at Risk?

Two newly disclosed critical PHP vulnerabilities could put websites at risk of serious security breaches—including websites powered by Concrete CMS.

On October 21, 2026, the PHP development team released emergency security updates addressing two critical vulnerabilities that could allow attackers to execute malicious code on vulnerable servers without logging in.

Both vulnerabilities received a CVSS 4.0 severity score of 9.2 out of 10, making them critical security concerns.

If your business website runs on Concrete CMS, there's an important question you should be asking:

Is your Concrete CMS website running a vulnerable version of PHP?

At Pixo Web Design & Strategy, we specialize in Concrete CMS development, maintenance, and security. We're offering a free initial Concrete CMS website security audit to help website owners identify potential risks and determine whether additional security updates or investigation may be needed.

What Are the Latest PHP Security Vulnerabilities?

The PHP development team identified two critical vulnerabilities:

• CVE-2026-109618: A memory corruption vulnerability involving out-of-memory handling that can potentially lead to remote code execution.

• CVE-2026-109619: A related vulnerability involving PHP's internal state handling that can also potentially allow remote code execution.

These vulnerabilities are particularly concerning because exploitation under affected conditions may not require a valid username or password.

An attacker who successfully exploits a vulnerable server could potentially execute unauthorized code and compromise the website or its underlying environment.

The PHP Foundation has advised PHP users to install the latest security updates immediately.

Why Concrete CMS Website Owners Should Pay Attention

Concrete CMS is a powerful, flexible content management system built using PHP.

That means its security depends not only on the Concrete CMS software itself but also on the PHP version, server configuration, installed packages, and hosting environment.

Even if your Concrete CMS installation is current, your website could still be at risk if its underlying PHP environment has not been patched.

The newly disclosed vulnerabilities affect PHP itself—not a security flaw specifically identified in Concrete CMS.

This distinction matters because updating Concrete CMS alone does not necessarily resolve vulnerabilities in the underlying PHP installation.

Which PHP Versions Are Affected?

The PHP development team released the following security updates on October 21, 2026.

Installations running earlier, unpatched versions in these branches may be vulnerable.

Older unsupported PHP versions also present security concerns and should be evaluated for migration to a supported release.

It's important to note that hosting providers may apply security backports to their own PHP packages. The displayed PHP version alone may not tell the complete story; the installed security patches must also be verified.

What Could Happen If Your Website Is Vulnerable?

A successful remote code execution attack can have serious consequences.

Depending on the server configuration and the attacker's access, potential consequences include:

Website Defacement

Attackers may be able to modify website content, redirect visitors, or replace legitimate pages with malicious content.

Customer Data Exposure

A compromised server could expose sensitive information, including customer records, form submissions, or database contents accessible to the affected application.

Malware Installation

Attackers could potentially install malicious scripts or establish unauthorized access to website files.

SEO Damage

Compromised websites can be used to publish spam pages, create malicious redirects, or distribute harmful content.

These activities can damage your search visibility and business reputation.

Website Downtime

Security incidents can disrupt normal website operations, potentially resulting in lost leads, sales, and customer confidence.

These are potential consequences of a successful compromise—not evidence that your website has been attacked.

How Do You Know If Your Concrete CMS Website Is Vulnerable?

Many website owners don't know which PHP version their website is using.

Even fewer know whether their hosting provider has applied the latest security patches.

Consider these questions:

1. Do you know which PHP version your Concrete CMS website uses?

2. Has your hosting provider installed the October 21, 2026 PHP security updates?

3. Is your Concrete CMS installation running a supported version?

4. Have your custom packages and third-party integrations been updated?

5. Do you have recent, verified website backups?

6. Has anyone reviewed your website's security configuration?

7. Would you know if suspicious activity occurred on your server?

If you're unsure about these answers, it's worth having your website evaluated.

A website that looks and functions normally can still have security weaknesses that aren't visible to visitors.

What Should Concrete CMS Website Owners Do Right Now?

The most important step is to verify that your PHP installation has received the appropriate security fixes.

If your server is running a vulnerable version, arrange for an immediate update with your hosting provider or development team.

Before making changes, it's also important to:

• Confirm that reliable backups are available.

• Verify PHP compatibility with your Concrete CMS installation.

• Review custom packages and integrations.

• Test changes to minimize website disruption.

• Review relevant security logs for suspicious activity.

• Confirm that security updates have actually been applied.

Don't wait for a routine website redesign or maintenance cycle to address a critical security vulnerability.

The PHP project has warned that there are no complete alternative mitigations for the two October 21 vulnerabilities. Applying the appropriate security fixes is essential.

Get a Free Concrete CMS Website Security Audit From Pixo

Not sure whether your Concrete CMS website is protected?

Pixo Web Design & Strategy is offering a free initial website security audit for Concrete CMS website owners.

Our team can help assess potential security concerns and identify whether your website may need additional attention.

An initial audit can include:

• Reviewing publicly identifiable website technologies

• Identifying visible signs of outdated software

• Checking publicly observable security configurations

• Reviewing HTTP security headers

• Identifying potential exposure of sensitive files or directories

• Providing recommendations for further security investigation

Where authorized server access is available, Pixo can also help verify the installed PHP version, security patch status, Concrete CMS compatibility, and relevant server configuration.

A public-facing audit alone cannot conclusively establish whether your PHP installation has received the necessary patches. Some checks require access to your hosting environment.

The free audit is an initial assessment, not a guarantee that every vulnerability or security incident will be detected.

Why Choose Pixo for Concrete CMS Security and Development?

Pixo Web Design & Strategy has been developing websites since 2003 and is one of the original Concrete CMS development companies.

Our experience extends beyond traditional website design to include custom PHP development, database integrations, advanced functionality, and ongoing website maintenance.

We understand how Concrete CMS interacts with the underlying technologies that power your website.

Our services include:

Concrete CMS Updates and Maintenance

Helping businesses maintain secure, compatible, and reliable Concrete CMS installations.

PHP Compatibility and Upgrades

Evaluating PHP versions, planning upgrades, and resolving compatibility issues with existing Concrete CMS websites.

Custom PHP Development

Updating custom functionality and integrations to work with modern PHP environments.

Website Security Improvements

Identifying potential weaknesses and recommending improvements to website configurations and maintenance practices.

Concrete CMS Website Redesign

Modernizing older websites with improved design, usability, performance, and security practices.

SEO, AEO, and GEO Optimization

Helping businesses improve search visibility while maintaining a technically sound website.

Our goal is to help you protect your website investment while keeping your online presence modern, functional, and effective.

Frequently Asked Questions About the PHP Security Vulnerabilities

Is Concrete CMS affected by the latest PHP vulnerabilities?

Concrete CMS websites may be affected if they run on vulnerable PHP installations. The vulnerabilities are in PHP itself rather than a confirmed flaw specific to Concrete CMS.

What are CVE-2026-109618 and CVE-2026-109619?

They are two critical PHP vulnerabilities disclosed in October 2026 that can potentially allow unauthenticated remote code execution under affected conditions.

How do I check my Concrete CMS PHP version?

Your hosting control panel or server administration tools may show the PHP version. Your hosting provider or Concrete CMS developer can also verify the version and whether security patches have been applied.

Will updating Concrete CMS fix the PHP vulnerabilities?

Not necessarily. These vulnerabilities require fixes to the PHP installation itself. Updating Concrete CMS does not automatically update the PHP runtime.

Can my website be vulnerable even if it looks normal?

Yes. Security vulnerabilities are not necessarily visible through the website's appearance or everyday functionality.

Does Pixo offer free Concrete CMS security audits?

Yes. Pixo is offering a free initial website security audit to help Concrete CMS website owners identify potential risks and determine whether additional investigation or updates are needed.

Is Your Concrete CMS Website Secure? Find Out Before There's a Problem.

The latest PHP security vulnerabilities are a reminder that website security requires ongoing attention.

Your website may be professionally designed, fast, and easy to manage—but if the underlying software hasn't received critical security updates, your business could still face unnecessary risks.

Don't assume your Concrete CMS website is protected. Verify it.

At Pixo Web Design & Strategy, we help Concrete CMS website owners identify potential security concerns, update outdated software, and maintain reliable websites.

Request Your Free Concrete CMS Security Audit

Let our experienced Concrete CMS developers help you determine whether your website needs attention.

Contact Pixo Web Design & Strategy for Your Free Website Security Audit

Protect your website. Protect your business. Stay ahead of emerging security threats.