CVE-2026-70554: Maxsite CMS

Critical severity, CVSS 9.8. EPSS: 1.2% chance of exploitation in the next 30 days.

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. Attackers can craft a malicious serialized PHP object payload delivered in a single HTTP request to trigger magic methods during object graph reconstruction, enabling property-oriented programming attacks or remote code execution via available gadget chains such as those targeting SoapClient or Imagick extensions.

Affected products

• Maxsite Maxsite CMS: from 0.78, up to and including 109.5

Published 2026-08-04. Last modified 2026-08-31.