CVE-2026-1542: Super Stage WP WordPress RCE Vulnerability

CVE-2026-1542 Overview

The Super Stage WP WordPress plugin through version 1.0.1 contains a PHP Object Injection vulnerability due to unsafe deserialization of user input. The plugin unserializes data from REQUEST parameters without proper validation, allowing unauthenticated attackers to inject arbitrary PHP objects. When a suitable gadget chain is present in the WordPress installation, this vulnerability can be leveraged to achieve various malicious outcomes including remote code execution, data manipulation, or denial of service.

Critical Impact

Unauthenticated attackers can exploit this PHP Object Injection vulnerability to potentially execute arbitrary code or manipulate application data when a compatible gadget chain exists in the WordPress environment.

Affected Products

• Super Stage WP WordPress plugin version 1.0.1 and earlier
• WordPress installations with Super Stage WP plugin active
• WordPress sites with additional plugins/themes containing exploitable gadget chains

Discovery Timeline

• 2026-02-28 - CVE-2026-1542 published to NVD
• 2026-03-02 - Last updated in NVD database

Technical Details for CVE-2026-1542

Vulnerability Analysis

This vulnerability falls under CWE-502 (Deserialization of Untrusted Data), a class of security flaws that occurs when applications deserialize data from untrusted sources without adequate validation. In the context of PHP applications, this manifests as PHP Object Injection, where attackers can instantiate arbitrary PHP objects by controlling serialized input passed to the unserialize() function.

The Super Stage WP plugin processes user-supplied data from REQUEST parameters (which includes GET, POST, and COOKIE data) and passes it directly to PHP's unserialize() function. This design flaw allows unauthenticated users to craft malicious serialized payloads that, when deserialized, instantiate objects of attacker-chosen classes with attacker-controlled properties.

The practical impact depends on the availability of "gadget chains" - sequences of magic methods (__wakeup(), __destruct(), __toString(), etc.) across classes in the application that can be chained together to achieve malicious outcomes. In WordPress environments with numerous plugins and themes, finding suitable gadget chains is often feasible.

Root Cause

The root cause of this vulnerability is the direct use of PHP's unserialize() function on user-controllable input without any validation, sanitization, or allowed class restrictions. The plugin fails to implement any of the standard mitigations for deserialization attacks, such as:

• Using safer data interchange formats (JSON, XML)
• Implementing allowlists for permitted classes via the allowed_classes option
• Validating input structure before deserialization
• Using HMAC signatures to verify data integrity

Attack Vector

The attack vector is network-based and requires no authentication or user interaction. An attacker can submit a crafted HTTP request containing a malicious serialized PHP object payload in REQUEST parameters. The attack flow typically involves:

1. Reconnaissance: The attacker identifies the Super Stage WP plugin is installed and enumerates other plugins/themes for potential gadget chains
2. Gadget Chain Construction: Using tools like PHPGGC or manual analysis, the attacker builds a serialized payload targeting available classes
3. Payload Delivery: The malicious payload is submitted via GET, POST, or COOKIE parameters
4. Exploitation: Upon deserialization, the injected objects trigger magic methods that execute the attacker's intended actions

The vulnerability is accessible without authentication, meaning any internet-facing WordPress site running the affected plugin version is potentially at risk.

Detection Methods for CVE-2026-1542

Indicators of Compromise

• Unusual serialized data patterns in web server access logs, particularly containing O: (object) notation in REQUEST parameters
• Unexpected outbound network connections from the web server process
• New or modified files in the WordPress installation directory
• Anomalous PHP process behavior or resource consumption
• Evidence of reverse shell connections or unauthorized command execution

Detection Strategies

• Monitor web application firewall (WAF) logs for requests containing serialized PHP object patterns (O:[0-9]+:")
• Implement log analysis rules to detect base64-encoded or URL-encoded serialized payloads in HTTP requests
• Deploy file integrity monitoring (FIM) on WordPress directories to detect unauthorized modifications
• Review WordPress access logs for requests targeting Super Stage WP plugin endpoints with suspicious parameters

Monitoring Recommendations

• Enable verbose logging for the WordPress installation and review logs for deserialization-related errors
• Configure intrusion detection systems to alert on common PHP Object Injection payload signatures
• Monitor for new scheduled tasks, user accounts, or plugin modifications that may indicate post-exploitation activity
• Implement network traffic analysis to detect command-and-control communications or data exfiltration

How to Mitigate CVE-2026-1542

Immediate Actions Required

• Deactivate and remove the Super Stage WP plugin immediately if it is not critical to site functionality
• Implement WAF rules to block requests containing serialized PHP object patterns targeting the affected plugin
• Review WordPress access logs for evidence of exploitation attempts
• Audit the WordPress installation for signs of compromise, including unauthorized files or modified content

Patch Information

At the time of publication, no official patch has been released for this vulnerability. Website administrators should monitor the WPScan Vulnerability Details page for updates regarding vendor patches or security advisories. Consider replacing the plugin with a secure alternative if no patch is forthcoming.

Workarounds

• Remove or deactivate the Super Stage WP plugin until a patch is available
• Deploy a Web Application Firewall (WAF) with rules to detect and block serialized PHP object payloads
• Restrict access to the WordPress admin area and plugin endpoints via IP allowlisting if possible
• Consider implementing a security plugin that provides additional input validation and request filtering

# WordPress CLI command to deactivate the vulnerable plugin
wp plugin deactivate super-stage-wp --path=/var/www/html/wordpress

# Verify plugin is deactivated
wp plugin list --status=active --path=/var/www/html/wordpress | grep -i "super-stage"