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Concrete CMS EUVDEUVD-2026-35994

| CVE-2026-10721 HIGH
Deserialization of Untrusted Data (CWE-502)
2026-06-10 ff5b8ace-8b95-4078-9743-eac1ca5451de GHSA-g82f-9pw7-773w
8.4
CVSS 4.0 · Vendor: ff5b8ace-8b95-4078-9743-eac1ca5451de
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Severity by source

Vendor (ff5b8ace-8b95-4078-9743-eac1ca5451de) PRIMARY
8.4 HIGH
CVSS:4.0/AV:L/AC:L/AT:N/PR:H/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:X/V:X/RE:X/U:X

Primary rating from Vendor (ff5b8ace-8b95-4078-9743-eac1ca5451de) · only source for this CVE.

CVSS VectorVendor: ff5b8ace-8b95-4078-9743-eac1ca5451de

CVSS:4.0/AV:L/AC:L/AT:N/PR:H/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:X/V:X/RE:X/U:X
Attack Vector
Local
Attack Complexity
Low
Privileges Required
High
User Interaction
None
Scope
X

Lifecycle Timeline

1
Analysis Generated
Jun 10, 2026 - 08:30 vuln.today

DescriptionCVE.org

Concrete CMS below 9.5.2 is vulnerable to PHP Object Injection via unserialize() calls in the  in Permission, Cache, and Search components. An unauthenticated attacker may trigger arbitrary PHP object instantiation if a malicious serialized payload has been placed in the database. Thanks XananasX7 for reporting.

AnalysisAI

PHP Object Injection in Concrete CMS versions below 9.5.2 allows arbitrary PHP object instantiation through unsafe unserialize() calls in the Permission, Cache, and Search components. The flaw is triggered when a malicious serialized payload has already been written to the database, meaning the unauthenticated trigger depends on a prior write primitive existing in the deployment. No public exploit identified at time of analysis, and CVSS 4.0 base scores it 8.4 with high confidentiality, integrity, and availability impact.

Technical ContextAI

Concrete CMS is a PHP-based open-source content management system. The root cause is CWE-502 (Deserialization of Untrusted Data): the Permission, Cache, and Search subsystems pass database-sourced strings into PHP's native unserialize() without validating that the input is structurally safe or originates from a trusted producer. Because PHP's unserialize() instantiates arbitrary classes and invokes magic methods such as __wakeup, __destruct, and __toString during reconstruction, an attacker who can control the serialized blob can drive a POP (property-oriented programming) gadget chain through whatever classes the Concrete CMS autoloader exposes, frequently leading to file write, SSRF, or RCE depending on the gadget surface. The advisory points to the 9.5.2 release notes as the fix boundary.

RemediationAI

Vendor-released patch: upgrade Concrete CMS to version 9.5.2 or later, which removes the unsafe unserialize() usage in the Permission, Cache, and Search components, per the release notes at https://documentation.concretecms.org/9-x/developers/introduction/version-history/952-release-notes. If immediate upgrade is not possible, restrict database write access to the application service account only and audit recent rows in the cache, permissions, and search index tables for entries beginning with PHP serialized markers such as 'O:' or 'a:' followed by class names that do not match expected application classes, removing or quarantining suspicious values; this carries the trade-off of potential cache or search index regeneration cost. Additionally restrict administrative access to the CMS using network ACLs or a WAF in front of /dashboard and disable any custom integrations that write user-influenced data into the affected tables, accepting that this reduces but does not eliminate exposure until 9.5.2 is applied.

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EUVD-2026-35994 vulnerability details – vuln.today

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