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Deserialization of Untrusted DataWeakness · CWE-502

CVE-2026-7888

HIGH · 8.4 CVSS v4.0 Published 2026-06-03
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
86/100
Remediation priority · High
Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
Concrete CMS below 9.5.2 is vulnerable to PHP Object Injection via unserialize() calls in the Workflow, Form block, and File/Set components that lack the allowed_classes restriction. 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 both independently reporting. 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.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

Concrete CMS below 9.5.2 contains PHP Object Injection vulnerabilities in Workflow, Form block, and File/Set components. The vulnerabilities stem from unserialize() calls that lack the allowed_classes restriction, allowing unserialize() to instantiate any PHP class. An attacker with database write access (PR:H) can place malicious serialized payloads in the database, which are then deserialized by the application, potentially leading to RCE via magic methods like __destruct or __wakeup.

MitigationUpgrade Concrete CMS to version 9.5.2 or later. Alternatively, apply code fixes to add allowed_classes parameter to all unserialize() calls in the affected components, restricting deserialization to only expected classes.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Local
Complexity
Low
Privileges
High
Authentication
X
User interaction
None
Scope
X

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

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Determine installed Concrete CMS version
    Access the Concrete CMS admin dashboard and navigate to Dashboard > System Information > Basics, or inspect the version.php file in the /config directory of your installation.
    Affected if The installed version is below 9.5.2 (for example, 9.5.1, 9.5.0, 9.4.x, 9.3.x, or earlier major versions).
  2. Identify use of vulnerable components
    Check if any of the following are in use or enabled in your installation: Workflow functionality (check /application/src/Concrete/Workflow or similar paths), Form block (check for blocks of type 'form' in the database or via the pages interface), and File/Set management features.
    Affected if Any of these components (Workflow, Form block, or File/Set) are actively used or installed on your site.
  3. Locate unserialize() calls in source code
    Search the application source code for unserialize() function calls, focusing on files within the Workflow, Form block, and File/Set directories. Use a command such as 'grep -rn "unserialize(" /path/to/concrete/ --include="*.php"' to identify these calls.
    Affected if You find unserialize() calls in any of the affected component files (Workflow, Form block, File/Set) that do not include the allowed_classes parameter.
  4. Verify allowed_classes parameter in unserialize calls
    Examine each unserialize() call identified in the affected components and check whether it includes the second parameter (allowed_classes). For example, look for patterns like unserialize($data, ['allowed_classes' => [...] ]) or unserialize($data, false).
    Affected if Any unserialize() call in the affected components either omits the second parameter entirely or does not properly restrict allowed_classes.
  5. Inspect database for suspicious serialized content
    Query the database for unusually long or encoded strings in tables related to Workflow, Form block (such as btForm tables), and File/Set (such as FileSetSavedSearches). Look for serialized PHP objects that may contain malicious payloads.
    Affected if You find unexpected serialized objects in database tables associated with these components, particularly objects that do not match expected class structures.

You are affected if your Concrete CMS installation is version 9.5.1 or below AND you use any of the Workflow, Form block, or File/Set components, with unserialize() calls lacking the allowed_classes restriction found in those components.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Upgrade Concrete CMS to version 9.5.2 or later. Alternatively, apply code fixes to add allowed_classes parameter to all unserialize() calls in the affected components, restricting deserialization to only expected classes.

Recommended fix High confidence

Concrete CMS 9.5.2

  1. Upgrade Concrete CMS to version 9.5.2 or later to resolve the PHP Object Injection vulnerability
  2. After upgrading, verify that the unserialize() calls in Workflow, Form block, and File/Set components now properly use the allowed_classes restriction
  3. Test the upgrade in a staging environment before deploying to production
  4. Ensure all serialized data in the database is from trusted sources, as the vulnerability requires malicious payload to already exist in the database

Generated from the published advisory — verify against the referenced sources before acting.

Have this fixed Scoped from the published advisory
  • Consultation2.0 h
  • Implementation4.0 h
  • Testing3.0 h
  • Review / QA2.0 h
11.0 hours of engineering $1,930
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-7888 in production — separate from our analysis above.

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
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  • Version or environment caveats, and links to real fixes
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