CVE-2019-25687: Pegasus CMS 1.0 RCE Vulnerability

CVE-2019-25687 Overview

CVE-2019-25687 is a critical remote code execution vulnerability affecting Pegasus CMS version 1.0. The vulnerability exists in the extra_fields.php plugin, which contains unsafe eval() functionality that allows unauthenticated attackers to execute arbitrary commands on the target system. By sending specially crafted POST requests to the submit.php endpoint with malicious PHP code in the action parameter, attackers can achieve code execution and potentially obtain an interactive shell on the vulnerable server.

Critical Impact

Unauthenticated remote code execution allowing attackers to gain full control of the affected web server through command injection via unsafe eval functionality.

Affected Products

• Pegasus CMS 1.0

Discovery Timeline

• 2026-04-05 - CVE CVE-2019-25687 published to NVD
• 2026-04-07 - Last updated in NVD database

Technical Details for CVE-2019-25687

Vulnerability Analysis

This vulnerability is classified under CWE-22 (Path Traversal), though the primary attack mechanism involves unsafe use of PHP's eval() function within the extra_fields.php plugin. The vulnerability allows unauthenticated attackers to inject and execute arbitrary PHP code through the application's submission endpoint.

The attack requires no authentication or user interaction, making it highly exploitable from a network context. An attacker can craft malicious HTTP POST requests targeting the submit.php endpoint, embedding PHP code in the action parameter. When the server processes this request, the injected code is passed to the unsafe eval() function, resulting in arbitrary command execution with the privileges of the web server process.

Successful exploitation can lead to complete server compromise, including data theft, installation of backdoors, lateral movement within the network, and use of the compromised server for further attacks.

Root Cause

The root cause of this vulnerability is the improper use of PHP's eval() function within the extra_fields.php plugin. The plugin fails to properly sanitize or validate user-supplied input before passing it to eval(), allowing attackers to inject arbitrary PHP code. This represents a fundamental secure coding violation, as eval() should never be used with untrusted input.

Attack Vector

The attack vector is network-based, requiring the attacker to send HTTP POST requests to the submit.php endpoint. The vulnerability can be exploited by:

1. Identifying a vulnerable Pegasus CMS 1.0 installation
2. Crafting a POST request to the submit.php endpoint
3. Including malicious PHP code in the action parameter
4. The unsafe eval() function executes the injected code
5. The attacker gains command execution on the server

For technical details on exploitation, see the Exploit-DB #46542 advisory.

Detection Methods for CVE-2019-25687

Indicators of Compromise

• Unusual POST requests to submit.php with suspicious payloads in the action parameter
• Web server logs showing encoded PHP functions like system(), exec(), passthru(), or shell_exec() in request parameters
• Unexpected outbound connections from the web server process
• New or modified files in the web root directory, particularly PHP files
• Evidence of webshell activity or reverse shell connections

Detection Strategies

• Implement web application firewall (WAF) rules to detect and block requests containing PHP code injection attempts
• Monitor web server access logs for POST requests to submit.php with anomalous or encoded content in parameters
• Deploy network intrusion detection systems (IDS) with signatures for common PHP code injection patterns
• Use file integrity monitoring (FIM) to detect unauthorized changes to web application files

Monitoring Recommendations

• Enable detailed logging on web servers hosting Pegasus CMS installations
• Monitor process creation events from the web server process for suspicious child processes
• Implement egress filtering to detect and alert on unexpected outbound connections
• Review server logs regularly for signs of exploitation attempts or successful compromise

How to Mitigate CVE-2019-25687

Immediate Actions Required

• Immediately disable or remove the extra_fields.php plugin from Pegasus CMS installations
• Consider taking vulnerable Pegasus CMS instances offline until a patch is available or alternative mitigations are in place
• Implement web application firewall rules to block requests to submit.php or filter dangerous parameter values
• Conduct forensic analysis on any systems that may have been exposed to determine if exploitation occurred

Patch Information

No official vendor patch information is currently available for this vulnerability. Organizations using Pegasus CMS 1.0 should monitor the Vulncheck Advisory for Pegasus CMS for updates. Given the age and severity of this vulnerability, organizations should strongly consider migrating to an actively maintained content management system.

Workarounds

• Disable or remove the vulnerable extra_fields.php plugin entirely
• Restrict access to submit.php at the web server level using IP-based access controls
• Implement strict input validation and output encoding for all user-supplied data if modifying the source code
• Place the Pegasus CMS installation behind a web application firewall with rules to block code injection attempts
• Consider isolating vulnerable systems in a network segment with restricted access

# Example Apache configuration to restrict access to submit.php
<Location /submit.php>
    Order deny,allow
    Deny from all
    # Allow only from trusted IP addresses if needed
    # Allow from 192.168.1.0/24
</Location>