CVE-2024-34070: Froxlor Stored XSS Vulnerability

CVE-2024-34070 Overview

CVE-2024-34070 is a Stored Blind Cross-Site Scripting (XSS) vulnerability identified in Froxlor, an open source server administration software. Prior to version 2.1.9, the Failed Login Attempts Logging Feature allows unauthenticated users to inject malicious scripts via the loginname parameter during login attempts. These malicious scripts are stored and subsequently executed when an administrator views the System Logs, creating a dangerous attack vector that requires no prior authentication.

Critical Impact

An unauthenticated attacker can inject malicious JavaScript that executes in the context of an administrator session, potentially allowing full application takeover by forcing the administrator to create attacker-controlled admin accounts.

Affected Products

• Froxlor versions prior to 2.1.9
• Froxlor Failed Login Attempts Logging Feature
• Froxlor System Logs viewing functionality

Discovery Timeline

• May 14, 2024 - CVE-2024-34070 published to NVD
• November 21, 2024 - Last updated in NVD database

Technical Details for CVE-2024-34070

Vulnerability Analysis

This Stored Blind XSS vulnerability resides in Froxlor's login failure logging mechanism. When a user attempts to log in with invalid credentials, the application logs the attempted loginname directly into the system logs without proper sanitization. The "blind" nature of this XSS means the attacker cannot immediately see the results of their injection—the malicious payload is stored and only executes when an administrator views the log entries through the administrative interface.

The attack is particularly severe because it requires no authentication to inject the payload, making it accessible to any external attacker. Once an administrator views the System Logs containing the malicious entry, the injected JavaScript executes within their authenticated session context, granting the attacker the ability to perform any action the administrator is authorized to perform.

Root Cause

The root cause of this vulnerability is improper input validation and output encoding of the loginname parameter in the Failed Login Attempts logging functionality. The application directly incorporated user-supplied input into log entries without sanitizing special characters or encoding the output when rendering logs in the administrative interface. This allows attackers to craft login attempts with JavaScript payloads embedded in the username field, which are then persisted and executed upon viewing.

Attack Vector

The attack is executed remotely over the network and requires user interaction from an administrator. An attacker submits login requests to the Froxlor login page with malicious JavaScript embedded in the loginname parameter. These requests are logged as failed login attempts. When an administrator navigates to the System Logs to review failed login attempts, the stored malicious script executes in their browser session. The attacker can leverage this to perform actions such as creating new administrator accounts, modifying server configurations, or exfiltrating sensitive data—all without the administrator's knowledge or consent.

// Vulnerable code - loginname directly included in log message
$rstlog = FroxlorLogger::getInstanceOf([
    'loginname' => $_SERVER['REMOTE_ADDR']
]);
$rstlog->logAction(FroxlorLogger::LOGIN_ACTION, LOG_WARNING, "Unknown user '" . $loginname . "' tried to login.");

// Fixed code - loginname removed from log message
$rstlog = FroxlorLogger::getInstanceOf([
    'loginname' => $_SERVER['REMOTE_ADDR']
]);
$rstlog->logAction(FroxlorLogger::LOGIN_ACTION, LOG_WARNING, "Unknown user tried to login.");

Source: GitHub Commit Changes

Additionally, the fix includes output sanitization when retrieving log entries:

// Additional fix - sanitize log text on output
while ($row = $result_stmt->fetch(PDO::FETCH_ASSOC)) {
    // clean log-text
    $row['text'] = preg_replace("/[^\w @#\"':.()[\]+\-_\/\\!]/i", "_", $row['text']);
    $result[] = $row;
}

Source: GitHub Commit Changes

Detection Methods for CVE-2024-34070

Indicators of Compromise

• Unusual or suspicious characters in the loginname field of failed login log entries, particularly <script>, javascript:, or encoded variants
• Log entries containing HTML tags, event handlers (e.g., onerror, onload), or encoded script payloads
• Unexpected administrator accounts created without legitimate authorization
• Browser-based anomalies reported by administrators when viewing System Logs

Detection Strategies

• Implement Web Application Firewall (WAF) rules to detect and block XSS payloads in login form submissions
• Monitor authentication logs for suspicious patterns in username fields that may indicate injection attempts
• Deploy Content Security Policy (CSP) headers to mitigate the impact of successful XSS exploitation
• Review administrator account creation audit logs for unauthorized additions

Monitoring Recommendations

• Enable detailed logging of all authentication attempts with payload inspection
• Configure alerts for login attempts containing special characters commonly used in XSS payloads
• Implement real-time monitoring of administrator privilege changes
• Regularly audit System Logs for signs of injection attempts or unusual patterns

How to Mitigate CVE-2024-34070

Immediate Actions Required

• Upgrade Froxlor to version 2.1.9 or later immediately
• Review existing System Logs for potential malicious entries and purge suspicious log records
• Audit administrator accounts for any unauthorized additions or modifications
• Implement network-level controls to restrict access to the Froxlor login page if possible

Patch Information

This vulnerability is fixed in Froxlor version 2.1.9. The patch addresses the issue through two mechanisms: first, by removing the user-supplied loginname from the log message entirely, and second, by implementing output sanitization using regex filtering when log entries are retrieved and displayed. Organizations should update to version 2.1.9 or later by following the official upgrade procedures. The security fix is available in commit a862307bce5cdfb1c208b835f3e8faddd23046e6. For detailed information, see the GitHub Security Advisory.

Workarounds

• Restrict access to the Froxlor administrative interface to trusted IP addresses only
• Disable or limit access to the System Logs functionality until patching is complete
• Implement a reverse proxy with XSS filtering capabilities in front of the Froxlor application
• Use browser extensions or security policies that block inline script execution for administrators

# Example: Restrict access to Froxlor admin panel via Apache
<Location "/froxlor">
    Require ip 10.0.0.0/8
    Require ip 192.168.0.0/16
</Location>