CVE-2023-39663
📋 TL;DR
MathJax versions up to 2.7.9 contain two regular expression denial-of-service (ReDoS) vulnerabilities in MathJax.js via the components pattern and markdownPattern. These vulnerabilities could allow attackers to cause denial of service by crafting malicious input that triggers inefficient regular expression processing. The vendor disputes the risk, claiming the regular expressions are not applied to user input.
💻 Affected Systems
- MathJax
📦 What is this software?
Mathjax by Mathjax
⚠️ Risk & Real-World Impact
Worst Case
Complete denial of service for applications using MathJax, making them unresponsive to legitimate users.
Likely Case
Degraded performance or temporary unavailability of MathJax rendering functionality.
If Mitigated
Minimal impact if proper input validation and rate limiting are implemented.
🎯 Exploit Status
No known public exploits; vendor disputes vulnerability exists.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Version 2.7.10 and later
Vendor Advisory: https://github.com/mathjax/MathJax/issues/3074
Restart Required: No
Instructions:
1. Update MathJax to version 2.7.10 or later. 2. Replace MathJax.js with the patched version. 3. Clear any caches that may serve old versions.
🔧 Temporary Workarounds
Input validation
allImplement strict input validation to prevent malicious patterns from reaching MathJax processing.
Rate limiting
allImplement rate limiting on requests that could trigger MathJax processing.
🧯 If You Can't Patch
- Implement web application firewall rules to block patterns that could trigger ReDoS.
- Monitor application performance for unusual CPU usage patterns.
🔍 How to Verify
Check if Vulnerable:
Check MathJax version in your application; if using version 2.7.9 or earlier, you may be vulnerable.Check Version:
Check the MathJax.js file header or package.json for version information.Verify Fix Applied:
Verify MathJax version is 2.7.10 or later and test with sample inputs that previously caused issues.📡 Detection & Monitoring
Log Indicators:
- Unusually high CPU usage when processing MathJax content
- Increased response times for pages using MathJax
Network Indicators:
- Multiple requests with complex patterns to MathJax endpoints
SIEM Query:
source="application_logs" AND (message="high cpu" OR message="slow response") AND component="MathJax"