What’s Vulnerable › Vulnerabilities

CVE-2021-36766

• Severity: high (CVSS 7.2 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 3.7% probability of exploitation in the next 30 days
• Public exploit or detection template: yes
• Published: 2021-07-30 · updated 2026-06-17
• Weakness: CWE-502

Description

Concrete5 through 8.5.5 deserializes Untrusted Data. The vulnerable code is located within the controllers/single_page/dashboard/system/environment/logging.php Logging::update_logging() method. User input passed through the logFile request parameter is not properly sanitized before being used in a call to the file_exists() PHP function. This can be exploited by malicious users to inject arbitrary PHP objects into the application scope (PHP Object Injection via phar:// stream wrapper), allowing them to carry out a variety of attacks, such as executing arbitrary PHP code.

Affected products

• Concrete CMS: before 8.5.6 — fixed in 8.5.6

How to fix

Upgrade to a fixed version: Concrete CMS 8.5.6. Check the vendor advisory for mitigations.

References

• http://packetstormsecurity.com/files/163564/Concrete5-8.5.5-Phar-Deserialization.html
• http://seclists.org/fulldisclosure/2021/Jul/36
• https://hackerone.com/reports/1063039
• http://packetstormsecurity.com/files/163564/Concrete5-8.5.5-Phar-Deserialization.html
• http://seclists.org/fulldisclosure/2021/Jul/36
• https://hackerone.com/reports/1063039

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