Deserialization of Untrusted Data Affecting concrete5/concrete5 package, versions <9.5.1
Threat Intelligence
The probability is the direct output of the EPSS model, and conveys an overall sense of the threat of exploitation in the wild. The percentile measures the EPSS probability relative to all known EPSS scores. Note: This data is updated daily, relying on the latest available EPSS model version. Check out the EPSS documentation for more details.
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- published27 Jun 2026
- disclosed21 May 2026
- creditUnknown
Introduced: 21 May 2026
CVE-2026-8135 (opens in a new tab)How to fix?
Upgrade concrete5/concrete5 to version 9.5.1 or higher.
Overview
concrete5/concrete5 is a concrete5 open source CMS.
Affected versions of this package are vulnerable to Deserialization of Untrusted Data via the ExpressEntryList block controller. An attacker can execute arbitrary code on the server by injecting a malicious serialized payload into the filterFields database column through the REST API, bypassing intended protection mechanisms. This is only exploitable if the attacker has administrator privileges with the ability to add blocks to an area.
Details
Serialization is a process of converting an object into a sequence of bytes which can be persisted to a disk or database or can be sent through streams. The reverse process of creating object from sequence of bytes is called deserialization. Serialization is commonly used for communication (sharing objects between multiple hosts) and persistence (store the object state in a file or a database). It is an integral part of popular protocols like Remote Method Invocation (RMI), Java Management Extension (JMX), Java Messaging System (JMS), Action Message Format (AMF), Java Server Faces (JSF) ViewState, etc.
Deserialization of untrusted data (CWE-502) is when the application deserializes untrusted data without sufficiently verifying that the resulting data will be valid, thus allowing the attacker to control the state or the flow of the execution.