CVE-2023-28333
📋 TL;DR
CVE-2023-28333 is a Mustache template injection vulnerability in Moodle's pix helper that could allow remote code execution if user input is improperly passed to the helper. The vulnerability affects Moodle installations using custom code that combines the pix helper with untrusted input. While the core Moodle LMS wasn't exploitable, custom plugins or themes could be vulnerable.
💻 Affected Systems
- Moodle LMS
📦 What is this software?
Fedora by Fedoraproject
Moodle by Moodle
Moodle by Moodle
Moodle by Moodle
Moodle by Moodle
Moodle by Moodle
Moodle by Moodle
Moodle by Moodle
Moodle by Moodle
⚠️ Risk & Real-World Impact
Worst Case
Remote code execution leading to complete system compromise, data theft, or ransomware deployment.
Likely Case
Limited impact since the core Moodle LMS wasn't exploitable; custom implementations might be vulnerable but require specific conditions.
If Mitigated
Minimal impact with proper input validation and patching in place.
🎯 Exploit Status
Exploitation requires custom code that passes user input to the pix helper, making it less likely in standard deployments.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Moodle 4.1.5, 4.0.9, 3.11.14, and 3.9.21
Vendor Advisory: https://moodle.org/mod/forum/discuss.php?d=445065
Restart Required: No
Instructions:
1. Backup your Moodle installation and database. 2. Download the patched version from moodle.org. 3. Replace the affected files or upgrade the entire installation. 4. Verify the fix by checking the version.
🔧 Temporary Workarounds
Input Validation for Custom Code
allEnsure any custom code using the pix helper properly validates and sanitizes user input before passing it to the helper.
🧯 If You Can't Patch
- Review and audit any custom plugins or themes for improper use of the pix helper with user input.
- Implement strict input validation and output encoding in custom code to prevent injection attacks.
🔍 How to Verify
Check if Vulnerable:
Check your Moodle version via the admin panel or by examining the version.php file in the Moodle root directory.Check Version:
grep -E "\$release|\$version" /path/to/moodle/version.phpVerify Fix Applied:
After patching, confirm the version is 4.1.5, 4.0.9, 3.11.14, or 3.9.21 or later.📡 Detection & Monitoring
Log Indicators:
- Unusual requests to Moodle endpoints involving the pix helper or template rendering.
Network Indicators:
- Suspicious payloads in HTTP requests targeting Moodle, especially with Mustache template syntax.
SIEM Query:
source="moodle_logs" AND (event="template_injection" OR message="pix_helper")🔗 References
- https://bugzilla.redhat.com/show_bug.cgi?id=2179422
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/3QZN34VSF4HTCW3C3ZP2OZYSLYUKADPF/
- https://moodle.org/mod/forum/discuss.php?d=445065
- https://bugzilla.redhat.com/show_bug.cgi?id=2179422
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/3QZN34VSF4HTCW3C3ZP2OZYSLYUKADPF/
- https://moodle.org/mod/forum/discuss.php?d=445065
