CVE-2021-27756
📋 TL;DR
This vulnerability in BigFix Compliance allows attackers to decrypt TLS-encrypted network traffic when TLS-RSA cipher suites are enabled without TLS 2.0 and secure ciphers. Attackers can passively record traffic and later decrypt it, exposing sensitive data. Organizations using BigFix Compliance up to version 2.0.5 are affected.
💻 Affected Systems
- HCL BigFix Compliance
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete decryption of all TLS-encrypted communications, exposing sensitive compliance data, credentials, and system information to attackers.
Likely Case
Partial decryption of intercepted traffic, potentially exposing sensitive compliance reports, configuration data, and authentication information.
If Mitigated
Minimal impact with proper TLS configuration and network segmentation, limiting exposure to encrypted data.
🎯 Exploit Status
Exploitation requires network access to intercept traffic but no authentication. Attack is passive and relies on weak cipher configuration.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Version 2.0.6 or later
Vendor Advisory: https://support.hcltechsw.com/csm?id=kb_article&sysparm_article=KB0096977
Restart Required: Yes
Instructions:
1. Download and install BigFix Compliance version 2.0.6 or later from HCL support portal. 2. Apply the update to all affected servers. 3. Restart the BigFix Compliance services. 4. Verify TLS configuration post-update.
🔧 Temporary Workarounds
Disable TLS-RSA cipher suites
allManually disable TLS-RSA cipher suites and enable only secure cipher suites with TLS 2.0.
# Configuration varies by platform - modify TLS settings in BigFix Compliance configuration files to disable RSA cipher suites and enable TLS 2.0 with secure ciphers
Network segmentation and encryption
allIsolate BigFix Compliance traffic to protected network segments and implement additional encryption layers.
# Use VPN or IPSec tunnels for all BigFix Compliance communications
# Implement network segmentation to restrict access to BigFix Compliance servers
🧯 If You Can't Patch
- Implement strict network segmentation to isolate BigFix Compliance traffic from untrusted networks
- Deploy network monitoring and intrusion detection systems to detect traffic interception attempts
🔍 How to Verify
Check if Vulnerable:
Check BigFix Compliance version and TLS configuration. Use tools like OpenSSL or Nmap to test if TLS-RSA cipher suites are enabled without TLS 2.0 and secure ciphers.Check Version:
# On BigFix Compliance server: bigfix_compliance --version or check installed package versionVerify Fix Applied:
Verify installation of version 2.0.6 or later and confirm TLS-RSA cipher suites are disabled with TLS 2.0 and secure ciphers enabled using SSL/TLS testing tools.📡 Detection & Monitoring
Log Indicators:
- Unusual network connection patterns
- Failed TLS handshake attempts
- Configuration changes to TLS settings
Network Indicators:
- Unencrypted or weakly encrypted traffic to/from BigFix Compliance servers
- Traffic interception patterns
SIEM Query:
source="bigfix_compliance" AND (event_type="tls_error" OR cipher_suite="RSA")