CVE-2023-46715
📋 TL;DR
This CVE allows authenticated IPSec VPN users with dynamic IP addressing to send spoofed packets appearing to come from other VPN users. It affects Fortinet FortiOS versions 7.4.0-7.4.1 and 7.2.6 and below. Attackers can impersonate other users but cannot receive responses to their spoofed packets.
💻 Affected Systems
- Fortinet FortiOS
📦 What is this software?
Fortios by Fortinet
⚠️ Risk & Real-World Impact
Worst Case
An attacker could impersonate another VPN user to send malicious traffic, potentially bypassing access controls or framing legitimate users for malicious activity.
Likely Case
Limited impact since attackers cannot receive responses to spoofed packets, preventing full session hijacking or data exfiltration via this method alone.
If Mitigated
With proper network segmentation and monitoring, impact is minimal as spoofed traffic can be detected and blocked.
🎯 Exploit Status
Requires authenticated VPN access and knowledge of other VPN user IPs; limited to sending only (no response receipt).
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: FortiOS 7.4.2 or 7.2.7
Vendor Advisory: https://fortiguard.com/psirt/FG-IR-23-407
Restart Required: Yes
Instructions:
1. Backup current configuration. 2. Download and install FortiOS 7.4.2 or 7.2.7 from Fortinet support portal. 3. Reboot the FortiGate device. 4. Verify version and VPN functionality.
🔧 Temporary Workarounds
Restrict VPN user IP assignment
allConfigure static IP addresses for VPN users instead of dynamic assignment to prevent exploitation.
config user local
edit <username>
set type password
set ip <static_ip>
end
🧯 If You Can't Patch
- Implement strict network segmentation to limit VPN user access to only necessary resources.
- Enable logging and monitoring for unusual VPN traffic patterns or IP spoofing attempts.
🔍 How to Verify
Check if Vulnerable:
Check FortiOS version via CLI: 'get system status' and verify if version is 7.4.0-7.4.1 or ≤7.2.6 with IPSec VPN enabled.Check Version:
get system status | grep VersionVerify Fix Applied:
After patching, confirm version is 7.4.2 or 7.2.7+ using 'get system status' and test VPN connectivity.📡 Detection & Monitoring
Log Indicators:
- Unusual VPN user IP changes
- Traffic from VPN IPs not matching assigned user mappings
Network Indicators:
- IPSec packets with mismatched source IP/user mappings
- Unidirectional traffic patterns from VPN users
SIEM Query:
source_ip IN vpn_ip_range AND NOT source_ip IN assigned_vpn_ips