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CVE-2026-70554

MaxSite CMS Unauthenticated PHP Object Injection via maxsite_comuser Cookie

Published: Aug 4, 2026Updated: Aug 31, 2026 Sources: CVE List NVDCWE-502
9.8CRITICAL
NVD MITRE
EPSS Score
0.9%
Top 44.2%
CISA KEV
Not in KEV
Exploits
No Known Exploits
Remediation
No Fix Available
Self-Check
Not available

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.

No summary for this CVE yet.

CVSS Vector Breakdown

AV:NAC:LPR:NUI:NS:UC:HI:HA:H
Exploitability
AV:NAttack Vector
Network
AC:LAttack Complexity
Low
PR:NPrivileges Required
None
UI:NUser Interaction
None
Scope
S:UScope
Unchanged
Impact
C:HConfidentiality
High
I:HIntegrity
High
A:HAvailability
High
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Weaknesses

CWE-502

Affected Products

MaxSite
commercialaka maxsite cms
MaxSite CMSOn-prem
Web & CMS Plugins / cms-core

Exploitability

No known exploits, KEV entries, or remediation guidance available for this vulnerability yet.
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Attack Graph

Products CVE Techniques Tactics

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MITRE ATT&CK

3 techniques
Execution
Initial Access
View detailed technique mapping

References

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

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