CVE-2025-66577
📋 TL;DR
This vulnerability in cpp-httplib allows attackers to spoof client IP addresses by sending malicious X-Forwarded-For or X-Real-IP headers. This can poison server logs, evade audit trails, and potentially influence authorization decisions. Any application using cpp-httplib versions before 0.27.0 with the vulnerable get_client_ip() function is affected.
💻 Affected Systems
- cpp-httplib
📦 What is this software?
Cpp Httplib by Yhirose
⚠️ Risk & Real-World Impact
Worst Case
Attackers completely evade detection by spoofing IP addresses in all logs, bypass IP-based authorization controls, and manipulate server metadata for further attacks.
Likely Case
Log poisoning leading to inaccurate audit trails, difficulty in forensic investigations, and potential evasion of basic IP-based rate limiting.
If Mitigated
Limited impact if proper IP validation and logging controls are already implemented separately from the vulnerable function.
🎯 Exploit Status
Exploitation requires only sending HTTP requests with malicious headers, making this trivial to weaponize.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 0.27.0
Vendor Advisory: https://github.com/yhirose/cpp-httplib/security/advisories/GHSA-gfpf-r66f-5mh2
Restart Required: Yes
Instructions:
1. Update cpp-httplib to version 0.27.0 or later. 2. Replace the vulnerable header file in your project. 3. Recompile and restart all affected services.
🔧 Temporary Workarounds
Implement custom IP validation
allReplace get_client_ip() with custom function that validates X-Forwarded-For and X-Real-IP headers against trusted proxies
Web server proxy configuration
linuxConfigure reverse proxies (nginx, Apache) to strip or validate X-Forwarded-For headers before they reach the application
# nginx example: proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for; # Only if from trusted proxy
🧯 If You Can't Patch
- Implement network-level IP validation using firewalls or WAFs to filter suspicious X-Forwarded-For patterns
- Enhance logging to capture both original and forwarded IP addresses for correlation
🔍 How to Verify
Check if Vulnerable:
Check if your code uses get_client_ip() from cpp-httplib and verify the version is below 0.27.0Check Version:
Check your cpp-httplib header file for version information or examine project dependenciesVerify Fix Applied:
Test that X-Forwarded-For and X-Real-IP headers are properly validated or ignored after update📡 Detection & Monitoring
Log Indicators:
- Mismatch between client IP in access logs and network connection logs
- X-Forwarded-For headers from untrusted sources
Network Indicators:
- HTTP requests with multiple X-Forwarded-For headers
- Requests from internal IPs claiming external origins
SIEM Query:
source="web_logs" | search X-Forwarded-For="*" | where client_ip != last(split(X-Forwarded-For, ","))