Pegasus CMS RCE (CVE-2019-25687)

Overview

A critical vulnerability in Pegasus CMS version 1.0 allows unauthenticated attackers to execute arbitrary commands on the underlying server. The flaw, tracked as CVE-2019-25687, resides in the extra_fields.php plugin and is remotely exploitable with no user interaction required.

Vulnerability Details

The vulnerability stems from unsafe use of the eval() function within the plugin’s code. Attackers can send a specially crafted POST request to the submit.php endpoint. By injecting malicious PHP code into the action parameter, they can bypass intended controls. This exploit grants the attacker the ability to run any operating system command, typically leading to a full compromise of the web server. The attack complexity is low, making it easily weaponizable.

Impact

The impact of this vulnerability is severe. Successful exploitation grants an attacker complete control over the affected web server. This can lead to:

• Deployment of a persistent interactive shell for ongoing access.
• Theft of sensitive data, including databases and user credentials.
• Use of the server as a pivot point to attack other internal network resources.
• Installation of malware, cryptocurrency miners, or ransomware.

Given the high volume of CMS-related attacks, systems left unpatched are at immediate risk. For context on how such breaches unfold, recent data breach reports are available at breach reports.

Remediation and Mitigation

The primary and only complete remediation is to apply the official patch from the vendor. If a patch is not immediately available, consider the following urgent actions:

1. Immediate Isolation: If patching is delayed, take the affected Pegasus CMS instance offline or restrict network access to it.
2. Temporary Mitigation: As an interim measure, disable or delete the vulnerable extra_fields.php plugin. However, this may break site functionality and is not a substitute for patching.
3. Comprehensive Update: Upgrade Pegasus CMS to the latest secure version as soon as it is released by the vendor. Do not rely on version 1.0.
4. Investigate for Compromise: Assume any unpatched system has been compromised. Review server logs for suspicious POST requests to submit.php, check for unknown files or processes, and consider a full system restore from a known-clean backup.

Stay informed on emerging threats by monitoring security news.

Security Insight

This flaw is a textbook example of the persistent danger of unsafe functions like eval() in web applications, a class of vulnerability often seen in older or less-maintained CMS platforms. It highlights how a single vulnerable plugin can completely undermine the security of an entire application, emphasizing the need for rigorous code review in third-party components, even in smaller-scale software.

Further Reading

• All Critical Vulnerabilities
• Recent Critical Vulnerabilities
• Top Critical CVEs