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Vulnerability record · CVE-2026-70554 · published 4 August 2026

CVE-2026-70554: Deserialization of untrusted data vulnerability

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.

9.3 CVSS 4.0 Critical EPSS 1.2% · top 32.2% CWE-502 · Deserialization of untrusted data Deferred
9.3CVSS 4.0 base score
1.2%EPSS exploitation probability, 30 days
NoNot in CISA KEV
0Affected product versions listed by NVD
3References
31 Aug 2026Last modified by NVD

Description

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.

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:

References

LinkTags
https://github.com/maxsite/cms
https://max-3000.com/page/maxsite-cms-109-6
https://www.vulncheck.com/advisories/maxsite-cms-unauthenticated-php-object-injection-via-maxsite-comuser-cookie

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Source: NIST National Vulnerability Database (record CVE-2026-70554), CISA KEV, FIRST EPSS (scores of 2026-09-27). This page is refreshed as NVD updates the record.