CVE-2026-24398
📋 TL;DR
Hono framework's IP restriction middleware improperly validates IPv4 addresses, allowing attackers to bypass IP-based access controls by crafting malformed IP addresses with octet values outside the valid 0-255 range. This affects all Hono applications using IP restriction middleware before version 4.11.7.
💻 Affected Systems
- Hono
📦 What is this software?
Hono by Hono
⚠️ Risk & Real-World Impact
Worst Case
Attackers bypass IP whitelist/blacklist restrictions to access protected endpoints, potentially leading to unauthorized data access, privilege escalation, or service disruption.
Likely Case
Unauthorized access to endpoints protected by IP-based restrictions, potentially exposing internal APIs or administrative interfaces.
If Mitigated
Limited impact if additional authentication layers exist beyond IP restrictions, though IP-based controls become ineffective.
🎯 Exploit Status
Exploitation requires sending HTTP requests with specially crafted IP addresses in headers like X-Forwarded-For or similar.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 4.11.7
Vendor Advisory: https://github.com/honojs/hono/security/advisories/GHSA-r354-f388-2fhh
Restart Required: Yes
Instructions:
1. Update Hono dependency to version 4.11.7 or later. 2. Run 'npm update hono' or equivalent package manager command. 3. Restart the application server.
🔧 Temporary Workarounds
Implement custom IP validation
allReplace Hono's IP restriction middleware with custom middleware that validates IP addresses using proper regex patterns or IP validation libraries.
Use reverse proxy IP filtering
allConfigure web server or reverse proxy (nginx, Apache) to enforce IP restrictions before requests reach the Hono application.
🧯 If You Can't Patch
- Implement additional authentication layers (API keys, JWT tokens) for all endpoints currently protected only by IP restrictions.
- Deploy WAF rules to block requests with malformed IP addresses in headers.
🔍 How to Verify
Check if Vulnerable:
Check if Hono version is below 4.11.7 and if IP restriction middleware is used in the application code.Check Version:
npm list hono | grep honoVerify Fix Applied:
Verify Hono version is 4.11.7 or higher in package.json and test IP restriction functionality with edge-case IP addresses.📡 Detection & Monitoring
Log Indicators:
- Requests with unusual IP formats (e.g., 256.0.0.1, 0.0.0.256) reaching protected endpoints
- Failed IP restriction logs showing bypassed restrictions
Network Indicators:
- HTTP requests with X-Forwarded-For or similar headers containing invalid IP octet values
SIEM Query:
http.request.headers:X-Forwarded-For REGEXP "(25[6-9]|2[6-9]\d|[3-9]\d\d|\d{4,})\."