CVE-2026-7888

Deferred Deferred - Pending Action

PHP Object Injection in Concrete CMS

Publication date: 2026-06-03

Last updated on: 2026-09-11

Assigner: ConcreteCMS

Description

Concrete CMS below 9.5.3 is vulnerable to PHP Object Injection via unserialize() calls in the Workflow, Form block, and File/Set components that lack the allowed_classes restriction. The Form block and File/Set sinks were addressed in 9.5.2; the Workflow component sinks were addressed in 9.5.3. An unauthenticated attacker may trigger arbitrary PHP object instantiation if a malicious serialized payload has been placed in the database. Thanks XananasX7 and Sanjorn Keeratirungsan (dizconnect) for independently reporting the original components, and sh4d0byss for reporting the Workflow component wasn't fixed in 9.5.2. The Concrete CMS security team gave this vulnerability a CVSS v.4.0 score of 8.4 with vector 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.

CVSS Scores

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Meta Information

Published

2026-06-03

Last Modified

2026-09-11

Generated

2026-09-12

AI Q&A

2026-06-03

EPSS Evaluated

2026-09-11

NVD

CVE-2026-7888

EUVD

EUVD-2026-34164

Affected Vendors & Products

Vendor	Product	Version / Range
concrete_cms	concrete_cms	to 9.5.2 (exc)

Helpful Resources

Exploitability

CWE

KEV

CWE ID	Description
CWE-502	The product deserializes untrusted data without sufficiently ensuring that the resulting data will be valid.

Attack-Flow Graph

Executive Summary

CVE-2026-7888 is a security vulnerability in Concrete CMS versions below 9.5.2 involving PHP Object Injection. This occurs because unserialize() calls in the Workflow, Form block, and File/Set components do not restrict allowed_classes, allowing an attacker to instantiate arbitrary PHP objects if a malicious serialized payload is placed in the database.

Impact Analysis

This vulnerability can have a high impact on the affected system. An unauthenticated attacker with local access can exploit it to instantiate arbitrary PHP objects, potentially compromising confidentiality, integrity, and availability of the system.

Compliance Impact

The vulnerability in Concrete CMS allows PHP Object Injection, which can lead to high impacts on confidentiality, integrity, and availability of data.

Such impacts can potentially affect compliance with common standards and regulations like GDPR and HIPAA, which require protection of sensitive data and system integrity.

However, the provided information does not explicitly state the direct effects on compliance with these standards.

Mitigation Strategies

To mitigate the PHP Object Injection vulnerability in Concrete CMS versions below 9.5.2, you should upgrade to version 9.5.2 or later where the issue has been fixed.

The fix involves adding the allowed_classes restriction to the unserialize() calls in the Workflow, Form block, and File/Set components to prevent arbitrary PHP object instantiation.

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