CVE-2020-5844: Artica Pandora FMS RCE Vulnerability

CVE-2020-5844 Overview

CVE-2020-5844 is an authenticated remote code execution vulnerability affecting Pandora FMS v7.0 NG. The vulnerability exists in the index.php?sec=godmode/extensions&sec2=extensions/files_repo endpoint, which allows authenticated administrators to upload malicious PHP scripts. Attackers can subsequently execute these scripts by leveraging base64 decoding of the file location, leading to arbitrary code execution on the underlying server.

Critical Impact

Authenticated administrators can achieve full remote code execution on the Pandora FMS server, potentially compromising the entire monitoring infrastructure and any systems it manages.

Affected Products

• Artica Pandora FMS 7.0 NG
• Pandora FMS v7.0NG.742_FIX_PERL2020

Discovery Timeline

• 2020-03-16 - CVE-2020-5844 published to NVD
• 2024-11-21 - Last updated in NVD database

Technical Details for CVE-2020-5844

Vulnerability Analysis

This vulnerability is classified as CWE-434 (Unrestricted Upload of File with Dangerous Type). The flaw resides in the files repository extension functionality within the Pandora FMS administrative interface. When an authenticated administrator accesses the vulnerable endpoint, they can bypass intended upload restrictions to introduce malicious PHP scripts into the server's file system.

The critical weakness lies in the application's handling of uploaded files combined with a base64 decoding mechanism that can be manipulated to execute the uploaded content. This represents a dangerous combination of insufficient file type validation and improper handling of file paths, which together enable full code execution capabilities.

The vulnerability requires administrator-level authentication, but once that prerequisite is met, exploitation is straightforward. Given that Pandora FMS is a network monitoring solution that typically has visibility into critical infrastructure, successful exploitation could provide attackers with a strategic foothold for lateral movement across an organization's network.

Root Cause

The root cause is inadequate validation of uploaded files in the files_repo extension module. The application fails to properly restrict the types of files that can be uploaded through the administrative interface. Additionally, the base64 decoding functionality used for file location handling introduces an exploitation vector that allows attackers to bypass security controls and execute arbitrary PHP code.

Attack Vector

The attack is network-based and requires the attacker to have valid administrator credentials for the Pandora FMS console. The exploitation process involves:

1. Authenticating to the Pandora FMS administrative interface with valid administrator credentials
2. Navigating to the files repository extension at index.php?sec=godmode/extensions&sec2=extensions/files_repo
3. Uploading a malicious PHP script that contains attacker-controlled code
4. Triggering execution of the uploaded script through base64 decoding manipulation of the file path

The GitHub PoC repository and Packet Storm advisory provide technical details on the exploitation methodology.

Detection Methods for CVE-2020-5844

Indicators of Compromise

• Suspicious HTTP requests to index.php?sec=godmode/extensions&sec2=extensions/files_repo with file upload activity
• Newly created PHP files in the Pandora FMS extensions or upload directories
• Unexpected PHP files containing base64-encoded content or obfuscated code
• Web server logs showing access to unusual PHP files outside normal application paths
• Process execution anomalies originating from the web server user context

Detection Strategies

• Monitor web server access logs for requests to the files_repo endpoint followed by execution of unfamiliar PHP files
• Implement file integrity monitoring on Pandora FMS directories to detect unauthorized file creation
• Deploy endpoint detection solutions to identify suspicious PHP process spawning or command execution
• Analyze network traffic for unusual outbound connections from the Pandora FMS server

Monitoring Recommendations

• Enable verbose logging for all administrative actions within Pandora FMS
• Configure alerts for file uploads through the administrative interface
• Implement application-layer monitoring to detect base64-encoded payloads in requests
• Review authentication logs for administrator account compromise indicators

How to Mitigate CVE-2020-5844

Immediate Actions Required

• Upgrade Pandora FMS to a version released after v7.0NG.742_FIX_PERL2020 that addresses this vulnerability
• Restrict network access to the Pandora FMS administrative interface to trusted IP addresses only
• Audit administrator accounts and enforce strong authentication mechanisms including multi-factor authentication
• Review recent file uploads and administrative actions for signs of exploitation
• Implement web application firewall rules to block malicious file uploads

Patch Information

Artica has addressed this vulnerability in subsequent releases of Pandora FMS. Organizations should upgrade to the latest stable version available from the official Pandora FMS website. After patching, administrators should audit the system for any indicators of prior compromise.

Workarounds

• Implement network segmentation to restrict administrative interface access to management VLANs only
• Deploy a reverse proxy with file upload inspection capabilities in front of Pandora FMS
• Disable the files repository extension if not required for operational purposes
• Implement strict file upload policies at the web server level to reject PHP file uploads
• Enable SELinux or AppArmor policies to restrict the web server's ability to execute uploaded files

# Example: Restrict access to administrative endpoints via Apache configuration
<Location "/index.php">
    <If "%{QUERY_STRING} =~ /sec=godmode/">
        Require ip 10.0.0.0/8 192.168.1.0/24
    </If>
</Location>