CVE-2025-54001 CRITICAL

CVE-2025-54001: WordPress Classter theme <= 2.5 - PHP Object Injection vulnerability

Vendor Themerex

Product Classter

Weakness CWE-502 · Unsafe deserialization

Published March 5, 2026

Last update April 28, 2026

View on NVD All CVEs

CVSS base score

9.8/10

Attack vector Network

Attack complexity Low

Privileges required None

User interaction None

Confidentiality High

Integrity High

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

What the vulnerability does

01Description

Deserialization of Untrusted Data vulnerability in ThemeREX Classter classter allows Object Injection.This issue affects Classter: from n/a through <= 2.5.

Explanation of Vulnerability in Simple Terms

02Summary

Classter versions 2.5 and earlier contain a deserialization vulnerability that allows unauthenticated attackers to execute arbitrary code on the server. The vulnerability exists in how the application processes untrusted serialized data without proper validation. An attacker can exploit this remotely without user interaction to gain full control of the affected system.

What an attacker can do

03Attacker Capabilities

Run arbitrary code on the server, read/modify all data, and take complete control of the site.

Potential impact on your site

04Site Impact

Complete compromise of the Classter installation and underlying server; all data at risk.

Conditions required to exploit

05Prerequisites

Network access only; no authentication or user interaction required.

Key dates

06Disclosure timeline

March 5, 2026 CVE published

April 28, 2026 Record updated

External resources

07References

NVD — National Vulnerability Database https://nvd.nist.gov/vuln/detail/CVE-2025-54001 CWE — Common Weakness Enumeration https://cwe.mitre.org/data/definitions/502.html AskarLabs — CWE-502 write-up Deserialization of Untrusted Data

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