CVE-2025-8679
📋 TL;DR
This vulnerability allows attackers to bypass captive portal authentication in ExtremeGuest Essentials by performing repeated manual login attempts. Unauthenticated devices can gain unauthorized network access, with client MAC addresses appearing as usernames in logs despite no MAC authentication being enabled. Organizations using affected versions of ExtremeGuest Essentials with captive portal SSID configurations are at risk.
💻 Affected Systems
- ExtremeGuest Essentials
📦 What is this software?
Extremeguest Essentials by Extremenetworks
⚠️ Risk & Real-World Impact
Worst Case
Complete network compromise where attackers gain persistent unauthorized access to internal networks, potentially leading to lateral movement, data exfiltration, or launching further attacks from within the network perimeter.
Likely Case
Unauthorized users gain network access through captive portals, potentially consuming bandwidth, accessing internal resources, or conducting reconnaissance on the network.
If Mitigated
Limited impact with proper network segmentation and monitoring, where unauthorized access is quickly detected and contained before significant damage occurs.
🎯 Exploit Status
Exploitation requires manual brute-force procedure but is unauthenticated and relatively simple to execute.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 25.5.0
Vendor Advisory: https://extreme-networks.my.site.com/ExtrArticleDetail?an=000130289
Restart Required: Yes
Instructions:
1. Download ExtremeGuest Essentials version 25.5.0 or later from Extreme Networks support portal. 2. Backup current configuration. 3. Apply the update following Extreme Networks upgrade procedures. 4. Restart the ExtremeGuest Essentials service or system as required.
🔧 Temporary Workarounds
Disable vulnerable captive portal configurations
allTemporarily disable or reconfigure captive portal SSID settings that are vulnerable to brute-force attacks
Implement rate limiting on login attempts
allConfigure rate limiting or account lockout policies for captive portal authentication attempts
🧯 If You Can't Patch
- Implement network segmentation to isolate captive portal networks from critical internal resources
- Enable enhanced logging and monitoring for unusual authentication patterns or MAC address anomalies
🔍 How to Verify
Check if Vulnerable:
Check ExtremeGuest Essentials version via web interface or CLI. If version is below 25.5.0 and captive portal SSID is configured, the system is vulnerable.Check Version:
Check via ExtremeGuest Essentials web interface under System > About, or use appropriate CLI command for your deploymentVerify Fix Applied:
Verify version is 25.5.0 or higher and test captive portal authentication with repeated failed login attempts to ensure proper blocking occurs.📡 Detection & Monitoring
Log Indicators:
- Multiple failed login attempts from same MAC address
- Client MAC addresses appearing as usernames in authentication logs
- Successful authentication after numerous failed attempts
Network Indicators:
- Unusual network traffic from devices that bypassed captive portal
- MAC addresses accessing network resources without proper authentication records
SIEM Query:
source="extremeguest" AND (event_type="authentication_failure" AND count > 10) OR (username CONTAINS MAC_ADDRESS_PATTERN)