CVE-2025-5114: Easycorp Zentao RCE Vulnerability

CVE-2025-5114 Overview

A critical insecure deserialization vulnerability has been identified in Easycorp ZenTao Project Management System version 21.5_20250307. This vulnerability affects the Edit function within the Committer component, accessible via the file path /index.php?m=editor&f=edit&filePath=cGhhcjovLy9ldGMvcGFzc3dk&action=edit. The flaw allows attackers to manipulate the filePath parameter to trigger arbitrary object deserialization through Phar stream wrapper exploitation, potentially leading to remote code execution.

Critical Impact

Authenticated attackers can exploit the insecure deserialization vulnerability to execute arbitrary code on the target server, potentially gaining full control of the ZenTao installation and underlying system.

Affected Products

• Easycorp ZenTao version 21.5_20250307
• ZenTao Project Management System (zentaopms) with vulnerable Committer component

Discovery Timeline

• 2025-05-23 - CVE-2025-5114 published to NVD
• 2025-12-05 - Last updated in NVD database

Technical Details for CVE-2025-5114

Vulnerability Analysis

This vulnerability represents a classic Phar deserialization attack vector in PHP applications. The vulnerable endpoint accepts a filePath parameter that is processed by PHP's file handling functions without adequate validation. The base64-encoded value cGhhcjovLy9ldGMvcGFzc3dk decodes to phar:///etc/passwd, demonstrating the attack technique.

When PHP processes a Phar archive URI through stream wrappers, it automatically deserializes the metadata stored within the archive. If an attacker can upload a malicious Phar file disguised as another file type (such as an image) and then reference it via the vulnerable filePath parameter, the application will deserialize attacker-controlled objects, potentially triggering gadget chains that lead to remote code execution.

The vulnerability is classified under CWE-502 (Deserialization of Untrusted Data) and CWE-20 (Improper Input Validation), reflecting both the root deserialization issue and the insufficient validation of user-supplied file paths.

Root Cause

The root cause of this vulnerability lies in the insufficient validation of the filePath parameter within the Editor module's Edit function. The application fails to:

1. Properly sanitize or validate the file path input before processing
2. Restrict the use of PHP stream wrappers, particularly the phar:// wrapper
3. Implement allowlisting for acceptable file paths or protocols
4. Validate that the referenced file exists within expected directories

The application directly processes user-controlled input through PHP's file functions, which honor the Phar stream wrapper and automatically deserialize Phar metadata.

Attack Vector

The attack vector is network-based and requires low-privileged authentication. An attacker would typically execute this attack through the following approach:

1. Craft a malicious Phar archive containing a serialized payload with PHP gadget chains
2. Upload the Phar file to the server, potentially disguised as an allowed file type (e.g., image, PDF)
3. Access the vulnerable endpoint at /index.php?m=editor&f=edit with the filePath parameter pointing to the uploaded Phar file using the phar:// wrapper
4. The server processes the Phar stream wrapper, triggering deserialization of the malicious payload
5. Gadget chains within the application execute attacker-controlled code

The exploit has been publicly disclosed in a GitHub PoC Repository, increasing the risk of exploitation in the wild. The vendor was contacted about this disclosure but did not respond.

Detection Methods for CVE-2025-5114

Indicators of Compromise

• HTTP requests to /index.php?m=editor&f=edit containing phar:// in the filePath parameter
• Base64-encoded values in filePath parameter that decode to phar:// URIs
• Unusual file uploads with Phar archive signatures (__HALT_COMPILER()) disguised as other file types
• Web server logs showing access to the Editor module with anomalous file path patterns

Detection Strategies

• Implement Web Application Firewall (WAF) rules to detect and block requests containing phar:// stream wrapper references
• Monitor for base64-encoded strings in URL parameters that decode to suspicious protocols
• Deploy file integrity monitoring on ZenTao installation directories to detect unauthorized Phar files
• Configure intrusion detection systems to alert on deserialization attack patterns in HTTP traffic

Monitoring Recommendations

• Enable verbose logging for the ZenTao Editor module and Committer component
• Monitor PHP error logs for deserialization-related warnings or exceptions
• Implement real-time alerting for requests targeting vulnerable endpoints with unusual parameters
• Review authentication logs for accounts accessing the Editor functionality with suspicious patterns

How to Mitigate CVE-2025-5114

Immediate Actions Required

• Restrict access to the Editor module (/index.php?m=editor) to only trusted administrative users
• Implement input validation to block phar:// and other potentially dangerous stream wrappers in file path parameters
• Consider disabling the vulnerable Committer component if not required for business operations
• Apply network-level access controls to limit exposure of the ZenTao management interface

Patch Information

At the time of publication, the vendor (Easycorp) has not responded to disclosure attempts and no official patch has been released. Organizations should monitor the official ZenTao release channels for security updates. In the absence of a vendor patch, implementing the workarounds below is strongly recommended.

For additional technical details, refer to the GitHub vulnerability disclosure and VulDB entry #310090.

Workarounds

• Disable the phar stream wrapper in PHP configuration by adding stream_wrapper_unregister('phar') to application bootstrap
• Implement a custom input filter to validate and sanitize all file path parameters before processing
• Place ZenTao behind a reverse proxy with strict URI filtering to block suspicious filePath values
• Restrict file upload capabilities to prevent attackers from placing malicious Phar archives on the server

# PHP configuration to disable phar stream wrapper
# Add to php.ini or application configuration
# Option 1: Disable phar extension entirely if not needed
# In php.ini:
# extension=phar.so   # Comment out or remove this line

# Option 2: Disable phar stream wrapper at runtime
# Add to ZenTao's index.php or config file:
# stream_wrapper_unregister('phar');

# Web server access restriction example (Apache)
# Block access to vulnerable endpoint
<Location "/index.php">
    <If "%{QUERY_STRING} =~ /filePath=.*cGhhcjo/i">
        Require all denied
    </If>
</Location>