CVE-2019-6266
📋 TL;DR
CVE-2019-6266 affects Cordaware bestinformed Windows client versions before 6.2.1.0, allowing attackers to downgrade encrypted connections to cleartext due to insecure SSL certificate verification and access patterns. This vulnerability enables man-in-the-middle attacks where sensitive data transmitted between the client and server can be intercepted in plaintext. Organizations using vulnerable versions of this software for document management and collaboration are at risk.
💻 Affected Systems
- Cordaware bestinformed Microsoft Windows client
📦 What is this software?
Bestinformed by Cordaware
⚠️ Risk & Real-World Impact
Worst Case
Complete interception of all communications between bestinformed client and server, including sensitive documents, credentials, and business data, leading to data breach, intellectual property theft, and compliance violations.
Likely Case
Man-in-the-middle attackers intercepting document transfers, user credentials, and metadata, potentially leading to unauthorized access to confidential information and document repositories.
If Mitigated
Limited exposure with proper network segmentation, certificate pinning, and monitoring, though downgrade attacks remain possible if vulnerable clients connect to untrusted networks.
🎯 Exploit Status
SSL/TLS downgrade attacks are well-understood and tools like SSLstrip can be adapted; exploitation requires network position to intercept traffic.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 6.2.1.0
Vendor Advisory: https://www.detack.de/en/cve-2019-6265-6266
Restart Required: Yes
Instructions:
1. Download bestinformed client version 6.2.1.0 or later from Cordaware. 2. Uninstall previous versions. 3. Install the updated client. 4. Restart affected Windows systems. 5. Verify connections use proper SSL/TLS validation.
🔧 Temporary Workarounds
Network segmentation and monitoring
allIsolate bestinformed clients to trusted network segments and monitor for cleartext traffic on expected encrypted ports.
Certificate pinning enforcement
windowsConfigure systems to enforce certificate pinning for bestinformed connections using group policies or local security settings.
🧯 If You Can't Patch
- Block bestinformed client traffic on untrusted networks using firewall rules to prevent interception.
- Implement network-level SSL/TLS inspection and termination with proper certificate validation before forwarding to bestinformed servers.
🔍 How to Verify
Check if Vulnerable:
Check bestinformed client version in Windows Programs and Features; versions below 6.2.1.0 are vulnerable. Use network monitoring tools to test if SSL/TLS connections can be downgraded to cleartext.Check Version:
wmic product where name="bestinformed" get versionVerify Fix Applied:
Confirm client version is 6.2.1.0 or higher. Test with SSL/TLS interception tools to ensure connections reject invalid certificates and maintain encryption.📡 Detection & Monitoring
Log Indicators:
- Cleartext HTTP traffic on ports expected to be encrypted (e.g., 443)
- SSL/TLS handshake failures or certificate validation errors in client logs
- Unusual connection patterns or IP addresses in bestinformed logs
Network Indicators:
- HTTP traffic instead of HTTPS to bestinformed servers
- SSL/TLS protocol downgrade attempts in network captures
- Unexpected certificate authorities in SSL/TLS connections
SIEM Query:
source="bestinformed" AND (protocol="HTTP" OR ssl_validation="failed")