Summary
Concrete CMS is vulnerable to PHP Object Injection via unserialize() calls in the Workflow, Form block, and File/Set components
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. The Concrete CMS security team thanks XananasX7 and Sanjorn Keeratirungsan (dizconnect) for both independently reporting this ssue.
Impact
Untrusted serialized data is processed by a deserializer that can instantiate arbitrary objects or execute code as a side effect. Typical impact: arbitrary code execution or logic abuse.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
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Frequently Asked Questions
- What is CVE-2026-7888? CVE-2026-7888 is a high-severity insecure deserialization vulnerability in concrete5/concrete5 (composer), affecting versions < 9.5.2. It is fixed in 9.5.2. Untrusted serialized data is processed by a deserializer that can instantiate arbitrary objects or execute code as a side effect.
- Which versions of concrete5/concrete5 are affected by CVE-2026-7888? concrete5/concrete5 (composer) versions < 9.5.2 is affected.
- Is there a fix for CVE-2026-7888? Yes. CVE-2026-7888 is fixed in 9.5.2. Upgrade to this version or later.
- Is CVE-2026-7888 exploitable, and should I be worried? Whether CVE-2026-7888 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2026-7888 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2026-7888? Upgrade
concrete5/concrete5to 9.5.2 or later.