CVE-2026-26047
📋 TL;DR
This vulnerability allows authenticated Moodle users to craft malicious TeX formulas that consume excessive server resources when rendered, potentially causing denial-of-service conditions. It affects Moodle installations using the mimetex TeX rendering component with insufficient execution time limits.
💻 Affected Systems
- Moodle
📦 What is this software?
Moodle by Moodle
Moodle by Moodle
Moodle by Moodle
⚠️ Risk & Real-World Impact
Worst Case
Complete service outage of Moodle instance due to resource exhaustion, affecting all users and potentially requiring server restart.
Likely Case
Degraded performance and intermittent service disruptions affecting user experience and learning activities.
If Mitigated
Minimal impact with proper resource limits and monitoring in place.
🎯 Exploit Status
Exploitation requires authenticated user access to submit TeX formulas. Attack complexity is low once authenticated.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Check Moodle security advisories for specific patched versions
Vendor Advisory: https://moodle.org/security/
Restart Required: No
Instructions:
1. Check Moodle security advisory for CVE-2026-26047
2. Update to patched Moodle version
3. Verify mimetex configuration has proper execution limits
🔧 Temporary Workarounds
Configure mimetex execution limits
allSet strict CPU/time limits for mimetex processes to prevent resource exhaustion
Configure in Moodle admin settings or server environment (specific commands depend on OS and configuration)
Disable mimetex rendering
allTemporarily disable mimetex TeX rendering if not essential
Modify Moodle configuration to use alternative TeX renderer or disable TeX support
🧯 If You Can't Patch
- Implement strict resource limits for mimetex processes at OS level
- Monitor server resource usage and set alerts for abnormal mimetex activity
🔍 How to Verify
Check if Vulnerable:
Check Moodle version and mimetex configuration. If using vulnerable version with mimetex enabled, system is vulnerable.Check Version:
Check Moodle version via admin interface or version.php fileVerify Fix Applied:
Verify Moodle is updated to patched version and mimetex has proper execution limits configured.📡 Detection & Monitoring
Log Indicators:
- Unusually long mimetex process execution times
- High CPU/memory usage by mimetex processes
- Multiple failed TeX rendering attempts
Network Indicators:
- Increased server response times for pages with TeX content
- Service degradation during specific user sessions
SIEM Query:
Search for mimetex processes with abnormal execution duration or resource consumption patterns