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CVE-2026-70554

MaxSite CMS Unauthenticated PHP Object Injection via maxsite_comuser Cookie

CVSS 4.0 9.3 CRITICALCVSS 3.1 9.8 CRITICALCheck source for fixed versionsKEV status unknown

Original advisory

cve-program · CVE-2026-70554

Published

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.

Read the publisher's advisory

Affected versions, risk and source history

cve-program · CVE-2026-70554

Published

MaxSite CMS

Vendor product

Publisher's version information

Shown as published. These rules are not interpreted as NuGet package version ranges.

{
                    "defaultStatus": "affected",
                    "vendor": "MaxSite",
                    "product": "MaxSite CMS",
                    "versions": [
                        {
                            "status": "affected",
                            "version": "0.78",
                            "versionType": "custom",
                            "lessThanOrEqual": "109.5"
                        },
                        {
                            "status": "unaffected",
                            "version": "109.6",
                            "versionType": "custom"
                        }
                    ]
                }

Original source record · Cite this exact observation · Complete original publisher JSON