CVE-2025-56422: LimeSurvey RCE Vulnerability

CVE-2025-56422 Overview

A critical insecure deserialization vulnerability has been identified in LimeSurvey, an open-source survey application. This vulnerability exists in versions prior to v6.15.0+250623 and allows remote attackers to execute arbitrary code on the server without authentication. The flaw stems from improper handling of serialized data, enabling attackers to craft malicious payloads that are processed by the application, ultimately leading to full system compromise.

Critical Impact

Unauthenticated remote code execution allows attackers to gain complete control of affected LimeSurvey servers, potentially leading to data theft, service disruption, and lateral movement within networks.

Affected Products

• LimeSurvey versions prior to v6.15.0+250623

Discovery Timeline

• 2026-03-10 - CVE CVE-2025-56422 published to NVD
• 2026-03-11 - Last updated in NVD database

Technical Details for CVE-2025-56422

Vulnerability Analysis

This vulnerability is classified under CWE-502 (Deserialization of Untrusted Data). Insecure deserialization vulnerabilities occur when an application deserializes data from untrusted sources without proper validation. In PHP applications like LimeSurvey, this typically involves the unserialize() function processing user-controlled input, which can instantiate arbitrary objects and trigger magic methods that lead to code execution.

The network-accessible nature of this vulnerability means attackers can exploit it remotely without any prior authentication or user interaction. Once exploited, attackers can achieve complete compromise of confidentiality, integrity, and availability of the affected system.

Root Cause

The root cause lies in the application's failure to properly validate and sanitize serialized data before processing. When user-controlled input is passed directly to deserialization functions, attackers can inject specially crafted serialized objects containing malicious payloads. PHP object injection attacks typically leverage existing classes within the application (gadget chains) to achieve arbitrary code execution through magic methods such as __wakeup(), __destruct(), or __toString().

Attack Vector

The vulnerability is exploitable over the network, requiring no authentication or user interaction. An attacker can send a malicious HTTP request containing a crafted serialized PHP object to a vulnerable LimeSurvey endpoint. When the application deserializes this payload, it triggers a chain of method calls that ultimately execute attacker-controlled code on the server.

The exploitation process typically involves:

1. Identifying a vulnerable endpoint that accepts serialized data
2. Analyzing the application's codebase for usable gadget chains
3. Crafting a malicious serialized payload that chains existing classes
4. Sending the payload to achieve remote code execution

For detailed technical information, refer to the GitHub CVE-2025-56422 Advisory.

Detection Methods for CVE-2025-56422

Indicators of Compromise

• Unusual PHP serialized data patterns in HTTP request logs containing object injection signatures (e.g., O: followed by class names)
• Unexpected child processes spawned by the web server process
• New or modified files in web-accessible directories, particularly PHP files
• Anomalous outbound network connections from the LimeSurvey server

Detection Strategies

• Monitor web application logs for suspicious serialized object patterns in POST parameters and cookies
• Implement Web Application Firewall (WAF) rules to detect and block PHP serialized object injection attempts
• Deploy endpoint detection solutions to identify post-exploitation behavior such as reverse shells or persistence mechanisms
• Conduct regular vulnerability scanning of LimeSurvey installations to identify unpatched systems

Monitoring Recommendations

• Enable verbose logging for the LimeSurvey application to capture detailed request data
• Implement file integrity monitoring on the LimeSurvey installation directory to detect unauthorized modifications
• Monitor system process trees for unexpected command execution originating from the PHP process
• Review authentication logs for any anomalous administrative access following potential exploitation

How to Mitigate CVE-2025-56422

Immediate Actions Required

• Upgrade LimeSurvey to version v6.15.0+250623 or later immediately
• If immediate patching is not possible, consider temporarily taking the application offline or restricting network access
• Review server logs for any indicators of prior exploitation attempts
• Conduct a thorough security assessment of any potentially compromised systems

Patch Information

The vulnerability has been addressed in LimeSurvey version v6.15.0+250623. Organizations should update to this version or later to remediate the vulnerability. The patch likely implements proper input validation and restricts deserialization to safe classes only.

For more information, visit the LimeSurvey Official Website or review the GitHub CVE-2025-56422 Advisory.

Workarounds

• Implement network-level access controls to restrict access to LimeSurvey to trusted IP addresses only
• Deploy a Web Application Firewall (WAF) with rules to detect and block PHP object injection patterns
• If possible, disable or restrict access to endpoints that process serialized data until patching is complete
• Consider implementing additional PHP hardening measures such as disable_functions directives for dangerous functions

# Example: Restrict LimeSurvey access via nginx until patching
# Add to server block configuration
location / {
    # Allow only trusted networks
    allow 10.0.0.0/8;
    allow 192.168.0.0/16;
    deny all;
    
    # Additional security headers
    add_header X-Content-Type-Options nosniff;
    add_header X-Frame-Options DENY;
}