CVE-2026-70553 in MaxSite
Summary
by MITRE • 08/04/2026
MaxSite CMS contains a remote code execution vulnerability that allows unauthenticated attackers to inject arbitrary PHP code into the application configuration file by submitting crafted POST requests to the install endpoint after installation is complete. Attackers can supply a malicious db_dbprefix value containing a single quote to break out of a PHP string literal in application/config/database.php, appending attacker-controlled PHP statements that are executed by the web server on every subsequent request, resulting in persistent unauthenticated remote code execution as the web-server process user.
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Analysis
by VulDB Data Team • 08/05/2026
This vulnerability represents a critical remote code execution flaw in MaxSite CMS that exploits improper input validation during the installation process. The vulnerability stems from insufficient sanitization of user-supplied data when processing POST requests to the install endpoint, specifically targeting the db_dbprefix parameter that controls database prefix configuration. When attackers submit malicious input containing a single quote character, they can manipulate the PHP string literal construction within the application/config/database.php file, effectively breaking out of the intended configuration structure and injecting arbitrary PHP code.
The technical implementation of this vulnerability leverages classic injection patterns where attacker-controlled data is directly incorporated into executable code without proper escaping or validation. The single quote character serves as the delimiter breaking point in the PHP string literal context, allowing malicious payloads to be appended to the configuration file. This injection occurs during post-installation configuration updates rather than initial installation, making it particularly dangerous as the application appears to be fully functional and operational, masking the underlying compromise.
The operational impact of this vulnerability extends far beyond simple code execution capabilities, as it provides persistent access to systems with web-server privileges. Once successfully exploited, attackers can execute arbitrary PHP commands as the web server process user, typically running with limited but potentially elevated permissions depending on system configuration. This persistent access enables attackers to establish backdoors, exfiltrate sensitive data, escalate privileges through additional system weaknesses, or use the compromised server as a launch point for further network reconnaissance and lateral movement activities.
The vulnerability aligns with CWE-94, which describes improper validation of dangerous data within code generation contexts, and demonstrates characteristics consistent with ATT&CK technique T1059.007 for command and scripting interpreter usage in PHP environments. The attack vector requires only unauthenticated access to the application's install endpoint, making it particularly attractive to automated exploitation tools. Organizations should immediately implement mitigations including restricting access to installation endpoints, implementing proper input validation and sanitization measures, and conducting comprehensive security assessments of all installed CMS components.
Mitigation strategies should focus on immediate patching of affected versions, implementing network-level restrictions to prevent access to installation endpoints post-deployment, and deploying web application firewalls with rules specifically targeting suspicious PHP injection patterns. Additionally, organizations must establish robust input validation mechanisms that properly escape or sanitize all user-supplied data before incorporating it into configuration files or executable code contexts. Regular security audits of CMS installations should include verification of proper file permissions, monitoring for unauthorized modifications to configuration files, and implementation of intrusion detection systems capable of identifying suspicious PHP code execution patterns.
The persistent nature of this vulnerability means that even if an initial exploitation attempt is detected and mitigated, the attacker maintains long-term access through the injected code until the configuration file is manually repaired or replaced. This characteristic makes the vulnerability particularly concerning for environments where CMS applications are frequently updated or modified, as it can remain undetected for extended periods while providing continuous unauthorized access to system resources and data repositories.