CVE-2024-27613
📋 TL;DR
CVE-2024-27613 is an input validation vulnerability in Numbas editor versions before 7.3 that allows improper handling of themes and extensions. This could enable attackers to execute arbitrary code or access sensitive data. Organizations using Numbas editor for educational assessment creation are affected.
💻 Affected Systems
- Numbas editor
📦 What is this software?
Editor by Numbas
⚠️ Risk & Real-World Impact
Worst Case
Remote code execution leading to complete system compromise, data theft, or ransomware deployment.
Likely Case
Unauthorized file access, privilege escalation, or denial of service affecting assessment integrity.
If Mitigated
Limited impact with proper network segmentation and least privilege controls in place.
🎯 Exploit Status
Based on CWE-20 (Improper Input Validation), exploitation likely requires crafting malicious theme/extension files but no public exploit details available.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 7.3 and later
Vendor Advisory: https://www.numbas.org.uk/blog/2024/03/development-update-march-2024/
Restart Required: Yes
Instructions:
1. Backup current Numbas installation and data. 2. Download Numbas editor version 7.3 or later from official repository. 3. Replace existing installation with updated version. 4. Restart Numbas services. 5. Verify functionality.
🔧 Temporary Workarounds
Disable theme/extension loading
allTemporarily disable loading of external themes and extensions to prevent exploitation.
Modify Numbas configuration to set 'allow_external_themes' and 'allow_external_extensions' to false
Network isolation
allRestrict network access to Numbas editor instances.
Configure firewall rules to limit access to trusted IP addresses only
🧯 If You Can't Patch
- Implement strict file upload controls and validation for theme/extension files
- Deploy web application firewall with input validation rules for Numbas endpoints
🔍 How to Verify
Check if Vulnerable:
Check Numbas editor version in admin interface or configuration files. If version is below 7.3, system is vulnerable.Check Version:
Check Numbas admin panel or examine package.json/version files in installation directoryVerify Fix Applied:
Confirm version is 7.3 or higher and test theme/extension loading functionality.📡 Detection & Monitoring
Log Indicators:
- Unusual theme/extension loading attempts
- File system access to unexpected locations
- Error messages related to theme parsing
Network Indicators:
- Unusual outbound connections from Numbas server
- Requests to theme/extension endpoints with suspicious parameters
SIEM Query:
source="numbas.log" AND ("theme" OR "extension") AND ("error" OR "failed" OR "malformed")