CVE-2025-27110
📋 TL;DR
Libmodsecurity3 version 3.0.13 fails to decode HTML entities containing leading zeroes, potentially allowing attackers to bypass web application firewall rules. This affects any system using ModSecurity v3 with the vulnerable library version. The vulnerability could enable evasion of security controls designed to detect malicious web traffic.
💻 Affected Systems
- ModSecurity v3
- Libmodsecurity3
📦 What is this software?
Modsecurity by Trustwave
⚠️ Risk & Real-World Impact
Worst Case
Attackers successfully bypass WAF protections, delivering payloads that would normally be blocked, leading to successful attacks like SQL injection, XSS, or remote code execution.
Likely Case
Limited WAF bypass for specific encoded payloads, potentially allowing some attacks to evade detection while other security layers may still catch them.
If Mitigated
With proper defense-in-depth including application-level validation and other security controls, impact is reduced even if WAF bypass occurs.
🎯 Exploit Status
Exploitation requires crafting specific HTML entities with leading zeroes to bypass WAF rules. No public exploit code has been identified.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Version 3.0.14
Vendor Advisory: https://github.com/owasp-modsecurity/ModSecurity/security/advisories/GHSA-42w7-rmv5-4x2j
Restart Required: No
Instructions:
1. Update Libmodsecurity3 to version 3.0.14 or later. 2. Recompile/relink any applications using the library. 3. Verify the update was successful.
🔧 Temporary Workarounds
No workarounds available
allThe vendor advisory states no known workarounds exist for this vulnerability.
🧯 If You Can't Patch
- Implement additional application-level input validation and sanitization
- Deploy additional WAF or security controls in front of vulnerable systems
🔍 How to Verify
Check if Vulnerable:
Check Libmodsecurity3 version: If version is exactly 3.0.13, system is vulnerable.Check Version:
Check library version through your distribution's package manager or compile-time version information.Verify Fix Applied:
Verify Libmodsecurity3 version is 3.0.14 or higher after update.📡 Detection & Monitoring
Log Indicators:
- Unusual patterns of encoded HTML entities in web traffic
- Requests that should be blocked by WAF rules but aren't
Network Indicators:
- HTTP requests containing HTML entities with leading zeroes (e.g., <)
SIEM Query:
Search for web requests containing patterns like '�*[0-9]+;' in URI or POST data