CVE-2024-56527
📋 TL;DR
This vulnerability in TCPDF allows cross-site scripting (XSS) attacks through unescaped error messages. Attackers can inject malicious scripts that execute when users view error pages. Any application using TCPDF versions before 6.8.0 is affected.
💻 Affected Systems
- TCPDF
📦 What is this software?
Tcpdf by Tcpdf Project
⚠️ Risk & Real-World Impact
Worst Case
Complete compromise of user sessions, credential theft, and unauthorized actions performed on behalf of authenticated users through persistent XSS.
Likely Case
Session hijacking, cookie theft, and defacement of error pages with malicious content.
If Mitigated
Limited impact with proper content security policies and input validation in place.
🎯 Exploit Status
Exploitation requires triggering TCPDF errors with malicious input that gets reflected in error messages.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 6.8.0
Vendor Advisory: https://github.com/tecnickcom/TCPDF/commit/11778aaa2d9e30a9ae1c1ee97ff349344f0ad6e1
Restart Required: No
Instructions:
1. Update TCPDF to version 6.8.0 or later. 2. Replace the TCPDF library files with the patched version. 3. Test PDF generation functionality.
🔧 Temporary Workarounds
Input Validation
allValidate and sanitize all user input before passing to TCPDF functions.
Error Message Filtering
allImplement custom error handling that escapes HTML special characters before displaying error messages.
🧯 If You Can't Patch
- Implement Content Security Policy (CSP) headers to restrict script execution
- Disable detailed error messages in production environments
🔍 How to Verify
Check if Vulnerable:
Check TCPDF version in code or composer.json. If version is below 6.8.0, the system is vulnerable.Check Version:
grep -r "TCPDF_VERSION" /path/to/tcpdf/ or check composer.lock for "tecnickcom/tcpdf" versionVerify Fix Applied:
Verify TCPDF version is 6.8.0 or higher. Test error handling with malicious input to ensure proper escaping.📡 Detection & Monitoring
Log Indicators:
- Unusual error messages containing script tags or JavaScript code
- Multiple failed PDF generation attempts with suspicious parameters
Network Indicators:
- HTTP requests to TCPDF endpoints with encoded script payloads in parameters
SIEM Query:
source="web_server" AND ("TCPDF" OR "FPDF") AND ("error" OR "exception") AND ("<script>" OR "javascript:")