CVE-2026-70554 MaxSite CVE debrief

Who should care

Administrators and users of MaxSite CMS, as well as security teams responsible for monitoring and patching vulnerabilities in web applications, should be aware of this vulnerability and take necessary actions to prevent exploitation. This includes reviewing and applying patches or updates for MaxSite CMS, implementing input validation and sanitization for user-controlled data, and monitoring for suspicious activity related to the maxsite_comuser cookie. Additionally, security teams should consider using a web application firewall to detect and prevent attacks targeting this vulnerability. IT managers and CISOs should ensure that their security teams are aware of the vulnerability and are taking steps to mitigate it. Vulnerability management teams should prioritize patching or mitigating this vulnerability to prevent potential remote code execution attacks. Incident response teams should be prepared to respond to potential attacks targeting this vulnerability. Security awareness training teams should educate users about the risks associated with this vulnerability and the importance of patching and mitigation. Compliance teams should ensure that their organization's security policies and procedures are aligned with the recommended actions for mitigating this vulnerability. Penetration testing teams should test their organization's defenses against this vulnerability to identify potential weaknesses. Red teaming teams should consider this vulnerability as a potential attack vector during their exercises. Blue teaming teams should prioritize detecting and responding to potential attacks targeting this vulnerability. Threat intelligence teams should monitor for potential threats targeting this vulnerability and provide alerts to relevant stakeholders. Security architects should review their organization's architecture to ensure that it is resilient to attacks targeting this vulnerability. Compliance and audit teams should ensure that their organization's security controls are adequate to mitigate this vulnerability. Business stakeholders should be aware of the potential risks associated with this vulnerability and support the necessary efforts to mitigate it. The C-

Technical summary

MaxSite CMS contains a PHP object injection vulnerability that allows unauthenticated attackers to execute arbitrary code by passing attacker-controlled serialized data in the maxsite_comuser cookie directly to unserialize() without validation or class allowlisting. This vulnerability can be exploited by crafting a malicious serialized PHP object payload delivered in a single HTTP request, which can trigger magic methods during object graph reconstruction. This enables property-oriented programming attacks or remote code execution via available gadget chains such as those targeting SoapClient or Imagick extensions. To mitigate this vulnerability, organizations should prioritize patching or mitigating this vulnerability to prevent potential remote code execution attacks.

Defensive priority

Organizations using MaxSite CMS should prioritize patching or mitigating this vulnerability to prevent potential remote code execution attacks.

Recommended defensive actions

• Review and apply patches or updates for MaxSite CMS
• Implement input validation and sanitization for user-controlled data
• Monitor for suspicious activity related to the maxsite_comuser cookie
• Consider using a web application firewall to detect and prevent attacks
• Confirm whether affected product deployments exist in managed environments and assign an owner for follow-up
• Review the supplied official advisory or CVE record to validate affected scope, severity, and vendor guidance
• Plan vendor-supported updates or mitigations through normal change control where exposure is confirmed

Evidence notes

The CVE description indicates that MaxSite CMS contains a PHP object injection vulnerability that allows unauthenticated attackers to execute arbitrary code by passing attacker-controlled serialized data in the maxsite_comuser cookie directly to unserialize() without validation or class allowlisting. To verify, defenders should review the official CVE record and assess their exposure to this vulnerability. Additionally, they should check for any available patches or updates for MaxSite CMS and implement input validation and sanitization for user-controlled data.

Official resources