by Kastro
Paper/Archive/CVE-2026-70554

CVE-2026-70554

MaxSite MaxSite CMS — MaxSite CMS Unauthenticated PHP Object Injection via maxsite_comuser Cookie

EPSS 1%CVSS 9.8
critical.is priorityof 100
43
CVSS 9.8 (CNA)9.8 / 10 × 3029.4Not in CISA KEV+300.0EPSS percentile 69.0.690 × 2013.8No public exploit+100.0SSVC exploitation: none+100.0
Description · from the CVE record

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

ProductAffectedFixed inSource
MaxSite CMS0.78 – 109.5–CNA

Scores by source

VulnCheck (CNA)9.8CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
VulnCheck (CNA)9.3CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
CISA ADPSSVCExploitation: none · Automatable: yes · Technical impact: total

References

refgithub.com/maxsite/cmspatchmax-3000.com/page/maxsite-cms-109-6writeupvulncheck.com/advisories/maxsite-cms-unauthenticated-php-object-injection-via-maxsite-comuser-cookie