CVE-2022-27240
📋 TL;DR
CVE-2022-27240 is a buffer overflow vulnerability in the WebAuthn implementation of Glewlwyd SSO server. Attackers can exploit this to execute arbitrary code or crash the server. This affects all Glewlwyd SSO server deployments running vulnerable versions.
💻 Affected Systems
- Glewlwyd SSO Server
📦 What is this software?
Glewlwyd Sso Server by Glewlwyd Sso Server Project
⚠️ Risk & Real-World Impact
Worst Case
Remote code execution leading to complete system compromise, credential theft, and lateral movement within the network.
Likely Case
Denial of service through server crashes, potentially disrupting authentication services for all users.
If Mitigated
Limited impact if proper network segmentation and least privilege principles are implemented, though service disruption remains possible.
🎯 Exploit Status
The vulnerability is in WebAuthn assertion handling, which typically requires user interaction, but the buffer overflow itself can be triggered without authentication once the WebAuthn flow is initiated.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 2.6.2
Vendor Advisory: https://github.com/babelouest/glewlwyd/releases/tag/v2.6.2
Restart Required: Yes
Instructions:
1. Backup current configuration and database. 2. Stop the Glewlwyd service. 3. Download and install version 2.6.2 from the official repository. 4. Restore configuration if needed. 5. Start the Glewlwyd service. 6. Verify the service is running correctly.
🔧 Temporary Workarounds
Disable WebAuthn Authentication
allTemporarily disable WebAuthn authentication method to prevent exploitation while patching.
Edit Glewlwyd configuration file and remove or comment WebAuthn authentication methods
Restart Glewlwyd service after configuration change
🧯 If You Can't Patch
- Implement strict network segmentation to isolate Glewlwyd servers from critical systems
- Deploy web application firewall (WAF) rules to detect and block buffer overflow attempts in WebAuthn requests
🔍 How to Verify
Check if Vulnerable:
Check the Glewlwyd version: if it's 2.x and less than 2.6.2, it's vulnerable. Also check if WebAuthn is enabled in configuration.Check Version:
glewlwyd --version or check the web interface admin panelVerify Fix Applied:
Verify the version is 2.6.2 or higher using the version check command, and ensure the service starts without errors.📡 Detection & Monitoring
Log Indicators:
- Multiple failed WebAuthn authentication attempts
- Server crash logs with segmentation faults
- Unusually large WebAuthn assertion payloads in logs
Network Indicators:
- Large POST requests to WebAuthn endpoints
- Multiple connection attempts to WebAuthn URLs followed by service disruption
SIEM Query:
source="glewlwyd.log" AND ("webauthn" AND ("assertion" OR "crash" OR "segmentation fault"))