CVE-2026-54856 in RexCoin Plugin
Summary
by MITRE • 10/29/2026
Unauthenticated PHP Object Injection in RexCoin <= 1.2.6 versions.
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Analysis
by VulDB Data Team • 10/29/2026
The vulnerability identified as an unauthenticated PHP object injection flaw within RexCoin versions up to and including 1.2.6 represents a critical security deficiency that allows attackers to execute arbitrary code on the target server without requiring valid credentials. This type of vulnerability stems from the application's improper handling of user-supplied input, specifically data intended for deserialization processes. In PHP applications, object serialization is often used to store complex state or pass objects between different parts of an application or across requests. However, when this serialized data originates from untrusted sources and is passed directly into a function such as unserialize() without adequate validation or sanitization, it creates a dangerous attack vector. The attacker can craft a maliciously formatted string that, upon deserialization, instantiates specific PHP classes with pre-defined properties containing exploitable logic.
The technical mechanism behind this flaw relies on the existence of "gadget chains" within the application's dependencies or core codebase. A gadget chain is a sequence of methods in existing classes that can be chained together to achieve an unintended side effect, such as arbitrary file read/write, remote command execution, or denial of service. Because the injection point is unauthenticated, any external actor on the network can interact with this endpoint and trigger the deserialization process. This bypasses standard access controls entirely, making it one of the most severe types of web application vulnerabilities. The attacker constructs a serialized payload that exploits these internal class methods, effectively hijacking the execution flow of the PHP interpreter to perform actions intended only for authorized administrators or system processes.
From an operational perspective, the impact of this vulnerability is catastrophic. Successful exploitation typically leads to full remote code execution on the server hosting the RexCoin instance. This compromises the confidentiality, integrity, and availability of the entire system. Attackers can exfiltrate sensitive financial data stored in the database, modify transaction records to facilitate fraud, install backdoors for persistent access, or use the compromised server as a pivot point to attack other systems within the internal network. Given that RexCoin is likely involved with cryptocurrency operations, the potential for direct financial loss through manipulation of wallet balances or theft of private keys further elevates the severity of this issue beyond standard web application compromise.
This vulnerability aligns closely with Common Weakness Enumeration identifier CWE-502, which describes Deserialization of Untrusted Data. It also maps to several techniques within the MITRE ATT&CK framework for enterprise security, particularly T1059 Command and Scripting Interpreter if arbitrary code execution is achieved, or T1078 Valid Accounts if the attacker leverages the injection to escalate privileges after initial access. The lack of authentication required for exploitation places this in a high-risk category where automated scanning tools can easily identify and exploit the flaw across large networks.
Mitigation strategies must focus on immediate remediation and long-term defensive coding practices. The primary solution is to upgrade RexCoin to version 1.2.7 or later, where the developers have presumably patched the deserialization endpoint by implementing strict input validation, whitelisting allowed classes for deserialization, or replacing unsafe serialization methods with safer alternatives like JSON encoding which does not support object instantiation. For systems that cannot be immediately updated, network-level mitigations such as Web Application Firewalls can be configured to detect and block payloads containing common PHP serialized data patterns, although this is a less reliable defense than patching the application code directly. Additionally, developers should adhere to secure coding guidelines by never passing user-controlled input into deserialization functions and by implementing strict type checking for all incoming parameters to prevent such injection attacks in future iterations of the software.